The Scottish Conservatives' leader, David McLetchie, is refusing to release full details of his Holyrood expenses.
Mr McLetchie is remaining tight-lipped about taxi claims
Copies of his claims have been published in response to freedom of information requests, but with some items blacked out.
The Tories will not say if Mr McLetchie has billed parliament for taxi journeys to and from the law firm Tods Murray where he used to work.
But a spokesman insisted Mr McLetchie's charges were all above board.
He said: "All David's expense claims relate to parliamentary and constituency business. We are not going into individual details of journeys or destinations.
"The parliament has decided a set of disclosure requirements under the Freedom of Information Act, to take into account personal security and data protection, and they've decided what information should go out.
"We are not going to go into details of any specifics in terms of destinations or journeys because to do that would be to undermine the parliament's decision that applies to all MSPs."
Scottish Labour urged the Tory leader, who pursued former First Minister Henry McLeish over an expenses scandal, to release all the details about his claims.
A spokesman said: "If there is any suggestion that David McLetchie has been using parliamentary funds to subsidise his work as a lawyer he should come clean about that immediately."
Most of the destinations and the names of other people using Mr McLetchie's taxi account were edited.
A Scottish Executive spokesman said: "In applying the requirements of the Data Protection Act we consider that it is unfair to disclose the destinations of taxi journeys because in doing so we could reveal details that could compromise the safety and security of an individual."
Information commissioner Kevin Dunion has been asked to rule on whether all the facts should be made public.