Prime Minister Gordon Brown was called on last night to scrap the Scotland Office after it was branded the "most pointless department in Whitehall".

According to answers to parliamentary written questions, each of the department's 20 policy officers dealt with the equivalent of only two letters each from MPs and peers in the past year at a time when its spending on entertainment went up by a third.

The amount of parliamentary correspondence handled totalled just 39, which was even lower than the 51 the Pesticide Planning Directorate dealt with and the 68 the Rural Development Service received over the same period, said the Liberal Democrats. Despite its extremely low level of parliamentary correspondence, the department still managed to spend almost £18,000 on stationery.

The LibDems also discovered through ministerial answers that the department's press office managed to write an average of one press release per week during the past year. As of March, the Scotland Office had two press officers.

The party also highlighted how the department increased its spending on hospitality by 32%, rising to more than £23,000 in the past year; almost twice the amount spent by the Wales Office.

In a written parliamentary answer David Cairns, the Scotland Office Minister, explained that ministerial correspondence was "processed by two clerical officers, who also undertake wider administrative functions. Drafting ministerial replies is part of the role of a pool of around 20 policy officials in addition to their other duties".

Alistair Carmichael, the Liberal Democrats' Scottish spokes-man, who received the ministerial replies, said: "As tensions between Westminster and Holyrood grow, the Scotland Office appears to be more concerned with hosting soirees than communicating with Edinburgh.

"Employing 20 staff to write an average of two official letters each year is indefensible.

"The Scotland, Wales and Northern Ireland Offices should merge to create a Department for Nations and Regions, with a full-time seat at the cabinet table," insisted the MP for Orkney and Shetland.

Matthew Elliott of the Taxpayers' Alliance said the Scotland Office was a pre-devolutionary antique and should be abolished.

"The Scotland Office is now the most pointless department in Whitehall. Taxpayers shouldn't have to foot the bill for an office and staff who are a relic of the pre-devolution era," he said.

"When (Chancellor) Alistair Darling starts to wield the axe ahead of the Comprehensive Spending Review in the autumn, he should start with the Scotland Office." Last night, Mr Cairns replied, accusing the Liberal Democrats of "deliberately misusing statistics". He said: "Alistair Carmichael is just plain wrong. He is labouring under the delusion that the Scotland Office exists solely to answer letters from MPs when its remit is so much wider."

Mr Cairns, the MP for Inverclyde, said the Scotland Office was a small department spending very small sums of money in a very efficient way. "Alistair Carmichael is deliberately misusing statistics to make a hackneyed political point and wasting taxpayers' money by asking pointless parliamentary questions.

"The Scotland Office carries out an essential role on behalf of the people of Scotland in ensuring their voice is heard at the highest level in Westminster."

The new-look department was created in 1999 following the Scotland Act, which brought in Scottish devolution. Prior to this date, it was known as the Scottish Office, which was created in 1885. Today, the Scotland Office is officially described as "a distinct entity" within the Ministry of Justice.