Conservatives have complained to Gordon Brown and Rhodri Morgan over claims about a Welsh Tory activist who has defected to Labour.
David Anstee has left the Conservatives for Labour
A Labour statement had claimed David Anstee was in a group which drew up the Tory Welsh assembly election manifesto.
But Welsh Tory leader, Nick Bourne, denied it, and asked whether Labour would be reviewing its procedures.
In response, Labour said Tories had had a "terrible week" and urged Mr Bourne: "When in a hole, stop digging".
The row began after Labour unveiled Mr Anstee, a 26-year-old Tory activist from Rhondda, as its latest recruit, and issued a comment from the Prime Minister Gordon Brown, welcoming him to the party.
But in his letter to Mr Brown and First Minister Rhodri Morgan, Mr Bourne said the claim about Mr Anstee and the manifesto "is totally without foundation and massively overstates the role played by Mr Anstee".
He asked whether the Labour Party intended reviewing its procedures and what action would be taken in response to what Mr Bourne described as a "serious episode".
Mr Bourne's letter also said Mr Anstee had confirmed that his role in the party had been overstated.
BBC Wales has obtained a leaked copy of an e-mail sent by Mr Anstee to Mr Bourne in which he said he was "fearful that the wrong message has got out".
He described the story that he had helped draft the manifesto as "rubbish" and said he was "disappointed" at the way he had been portrayed.
Meanwhile, the Conservatives have apologised to Rhondda AM Leighton Andrews for saying he was responsible for the claims about Mr Anstee's role in drawing up the manifesto.
A Conservative spokesman said the party accepted that Mr Andrews, a deputy minister in the Welsh Assembly Government, did not personally make the claims.
The Tories also said that a threat to refer the matter to the commissioner for standards had been dropped.
Responding to Mr Bourne's letter, a Welsh Labour spokesman said: "I bet Nick Bourne wishes he had stayed on holiday in the south of France. This has been a terrible week for the Tories.
"First, one of their bright young talents defected to Labour, then Nick Bourne's chief of staff was forced to apologise to a Labour minister.
"Maybe the Tories should remember the well-worn phrase, 'When in a hole stop digging'."