The head of a government agency was criticised last night after he apparently snubbed an invitation to appear before a Holyrood committee.

Malcolm Reed, the chief executive of Transport Scotland, was scheduled to appear before the Transport, Infrastructure and Climate Change Committee to give evidence on the government's plans to abolish tolls on the Forth and Tay bridges.

But he failed to appear, prompting an angry outburst from Green MSP Patrick Harvie, the committee convener.

Mr Harvie accused Transport Scotland, which is responsible for delivering the government's £3bn capital investment programme, of turning down its invitation at the eleventh hour and said he would be demanding answers from John Swinney, Cabinet Secretary for Finance and Sustainable Growth, when he appears before the committee next week. He said: "I'm very disappointed at Transport Scotland's decision. To refuse an invitation to appear, at very short notice, is highly unusual and prompted great surprise from the committee.

"Several members expressed their concern and disappointment, and we will be writing to the minister to express this."

Mr Harvie added: "It is important to remember the parliament's committees have the authority to require witnesses to attend, but we're talking here about Scotland's transport agency - there is no reason why we should have to go as far as that.

"I'm sure that members will want to ask some very direct questions of the minister when he appears in front of the committee next week.

"It has been said it is for the minister to decide which of the government's officials give evidence, so I am sure that members will want to know whether or not the minister himself decided that Transport Scotland should not give evidence to the committee."

Liberal Democrat MSP Alison McInnes, another member of the committee, said she would also be seeking an explanation from Mr Swinney.

She said: "It must surely beg the question, what has Transport Scotland got to hide?"

Despite attempts to get a response from both the government and Transport Scotland last night, neither were able to provide a comment.