Labour finally got its campaign in Glasgow East up and running today in a by-election that could determine the future of Gordon Brown.

Margaret Curran, selected last night as Labour's candidate, took to the campaign trail in the constituency, followed by a posse of supporters bearing placards and balloons.

In a fighting speech she told them: "We have a job to do and the Labour fight-back starts right here, right now.

"I understand that the Labour Party must step up to the challenge in front of us.

"I am determined to lead that challenge and I will take the Labour Party forward."

Ms Curran, 49, a member of the Scottish Parliament and former Holyrood minister, was chosen last night as Labour's candidate after the previous front-runner pulled out citing family reasons.

The by-election on July 24 was caused by the resignation on health grounds of Labour MP David Marshall.

He had a majority of 13,500 over the SNP in 2005.

It would normally be viewed as a safe Labour seat but coming in the wake of by-election humiliations for Labour in Crewe and Henley, it is seen as crucial for Mr Brown's political future.

Moments after being selected last night, Ms Curran challenged SNP candidate John Mason to a live TV debate, a challenge he today accepted saying: "Absolutely - I would debate with Margaret every single day if she would like to."

In her speech today, perched on a wooden box on the pavement outside a Co-op store in Glasgow's Shettleston Road, Ms Curran made clear she would take the fight to the SNP, whom she accused of being "hand-in-hand" with the Tories and of being soft on anti-social behaviour and crime.

"I look forward to a very spirited campaign," she said.

"I fundamentally believe that in the east end of Glasgow we must make sure that their issues are represented in Westminster."

Answering media questions later Ms Curran insisted she would have no problem, if elected, in doing two jobs - that of MP and MSP.

"If you want a job done, ask a busy woman. If I'm that busy woman, I will do it," said Ms Curran, a former lecturer in community education.

But she also said the question of having two jobs would be resolved "in the short term".

She said she had no received a call from Gordon Brown but added: "When I win, I expect to have one."

And asked if she expected Mr Brown to visit her campaign she said that was a matter for him.

Ms Curran also ducked questions on whether she believed there should be an early referendum on Scottish independence, as advocated by former Scottish Labour leader Wendy Alexander.

"I am not frightened of the verdict of the Scottish people," she said, adding: "I don't think the Scottish people want independence. But my focus just now is on the issues that matter to the people - poverty, jobs and regeneration."

mfl Meanwhile, Liberal Democrat acting Scottish leader Michael Moore joined party candidate Ian Robertson for their campaign launch in the constituency this morning.

Mr Robertson, a maths teacher who was born and brought up in the east end of Glasgow, identified unemployment, housing and crime as being among the key issues in the campaign.

He also rejected claims that the by-election would be a straight fight between Labour and the Nationalists.

We have a job to do and the Labour fight-back starts right here, right now Margaret Curran

"It's not a two horse race - we're very much in it," he said.

"If you speak to people on the doorsteps who don't want to vote Labour this time - and I think the Labour vote is crumbling - what they're saying is they want a good candidate, a local candidate.

"They don't want to see the break-up of the United Kingdom."

He added that the Scottish Lib Dems' leadership race, after the surprise resignation of Nicol Stephen last week, would benefit his campaign.

"Leadership contests are great - it's an opportunity to discuss Liberal Democracy in Scotland. All that can do is raise my profile."

Mr Moore added that he expected all three leadership candidates - Ross Finney, Tavish Scott and Mike Rumbles - to visit the constituency and campaign for the party.

"Ian Robertson is going for one job, not two as Margaret Curran is."

Nationalist candidate John Mason visited a local post office in the Garrowhill area of the city today along with SNP MSPs Bob Doris, Bashir Ahmad, Sandra White and Bill Kidd to remind voters to register for postal votes by tomorrow.

The Glasgow councillor hit out at the early staging of the by-election with many local residents expected to be on holiday as part of the Glasgow Fair.

"The electorate, the people are being treated with contempt both with the timing of the campaign and the fact that Labour can't even produce a real candidate because they're talking about one voice for the whole east end when potentially there's two voices for the area."

First Minister Alex Salmond, the SNP leader, is currently MP for Banff and Buchan, as well as MSP for Gordon. He intends to stand down as the former at the next election.

But Mr Mason said that situation was different because Mr Salmond was "upfront" when he originally stood and was also "not standing in this election".

He added: "By-elections give the chance to change your vote from normal and send a message to the Government.

"It's still going to be the Labour Government the day after the 25th.

"It's a chance for people to send out a message - they're not changing the Government."

mfl The Tories seized on the SNP's criticism of Ms Curran, arguing that the same applied to Mr Salmond, who is both a Holyrood MSP and Westminster MP.

"I am delighted the candidate has issued this call - I entirely agree with him," said Scottish Tory leader Annabel Goldie.

"The first person who should respond to it is not Margaret Curran but Alex Salmond.

"I hope he will confirm immediately he is going to take his candidate's advice.

"If he can't take his candidate's advice, or his candidate can't speak with the leader's blessing, it just shows what a mess the SNP campaign is in."

Ms Goldie claimed her party was receiving a positive response on the doorsteps.

"In this seat it's very clear that people want change," she said.

"They identify Labour with failure but, because it's a Westminster election, people are clearly uneasy about furthering the cause of separatism.

"Although they want change, they are beginning to understand the Conservatives offer genuine and safe change.

"That is something we will be very clear about on the doorstep - we are a safe option for the voters of Glasgow East."