THE veteran Labour MP who raised questions about the leaked document falsely claiming that suggesting Nicola Sturgeon had told French diplomats she would prefer the Tories to form the next government, is to raise the subject again when the House of Commons resumes.

Paul Flynn, who represents the Welsh constituency of Newport West, told The National it was “extraordinary” that an inquiry into the leak – which was expected to be completed before last Thursday’s General Election – should still be continuing.

It is one of the thorniest subjects David Mundell, the Scottish Secretary, will have to deal with as he settles into his new job.

Details of the memo were published in a London newspaper early last month and purported to give a civil servant’s account of a meeting the First Minister had with the French ambassador.

Sturgeon said the contents were “100 per cent untrue”. The French diplomat confirmed that no such remark had been made.

Flynn is a long-standing member of the public administration select committee, which oversees the civil service.

Last month he urged the government to proceed rapidly with an inquiry into the leak, which he said had been “contrary to our long traditions of civil service impartiality”.

“This matter is one of great importance and I believe it requires urgent investigation. It is difficult to understand claims that it cannot be swiftly resolved and a conclusion published before 7 May,” Flynn wrote.

Cabinet Secretary Sir Jeremy Heywood replied: “I have instigated a Cabinet Office-led inquiry to establish how extracts from this document may have got into the public domain. I consider this a matter of the highest priority and am treating it with the appropriate urgency.

“Until that inquiry is complete, I will not be making any further comment on the document or the inquiry.”

Flynn retorted: “‘The highest priority’ and ‘appropriate urgency’ sound less like the speed of an arthritic sloth by which other government inquiries traditionally move.

“It is crucial for the reputation of the civil service that this issue should not be allowed to influence public opinion during the election on the basis of a possible untruth. An investigation involving very few people could be swiftly concluded.”

However, when contacted by The National yesterday, a Scotland Office spokesman said the inquiry was “still ongoing”.

Flynn told The National: “We can’t table parliamentary questions for about another week, but I will raise it at the first opportunity, whether that’s at the first question time or as an early day motion.

“It’s extraordinary that such a simple inquiry should take so long. The last I heard the leak had been narrowed down to one individual.

“The last thing we want is for it to become bogged down in procedure – we all know the years it took for the Bloody Sunday inquiry to eventually issue a report.

“I think there’s some chicanery here – it’s implausible that it is still ongoing.”

At the time of the leak Liberal Democrat Alistair Carmichael, who was Scottish Secretary, denied that it was embarrassing for his department, and said: “This is the middle of an election campaign, these things happen.”

In an interview shortly after the memo came into the public domain, Prime Minister David Cameron appeared to point the finger of blame at his Liberal Democrat coalition colleagues.

When asked if he suspected the LibDems, he replied: “I have heard very clearly David Mundell [the Tory Scotland Office minister] saying it wasn’t him, so one does wonder.”

One of Carmichael’s advisers was expected to be questioned by Cabinet Office officials.

According to the report of the memo’s contents, Sturgeon had said she did not see Ed Miliband as “prime ministerial material”.

After it was published, she complained of “dirty tricks” and emphatically denied expressing a preference for Cameron.