You should look after yourself, you need to watch out

Lord Cocks's advice to Elizabeth Filkin

In turn, Ms Filkin complains her request for an urgent meeting to discuss the independence of her post has been ignored.

The row over Ms Filkin's office erupted last year when she was not automatically appointed to the job.

Confidence fears

She complained the post was being downgraded and refused to reapply for it without guarantees over the independence of the office.

The episode sparked fears that public confidence would be lost in the ability of MPs to police their own rules.

The parliamentary commissioner quotes a former Labour chief whip advising her to "watch out" in the wake of her investigations into complaints about high profile MPs.

Michael Martin says the claims are not backed by evidence

Mr Martin has previously urged Ms Filkin to substantiate her allegations and repeats that complaint in the newly published correspondence.

Ms Filkin's letters "identify no names and do not provide the evidence which your allegations would lead one to expect".

Ms Filkin told the BBC she had already provided detailed information on her concerns.

But she insisted she had never made allegations as such and that her only concern was, and is, the independence of the office.

Despite her refusal to name names, Ms Filkin does quote the late Lord Cocks, a former Labour chief whip.

Lord Cocks told her: "You should look after yourself, you need to watch out ... A lot of stuff is going to hit the fan soon."

'Sustained campaign'

Last month, Labour MP David Winnick, who has been a prominent defender of Ms Filkin, said the three main political parties were guilty of a witch-hunt against her.

He said: "There is no doubt at all in my mind that the parliamentary commissioner for standards has been the subject of a sustained campaign to get her out of her job.

"This campaign has been going on almost from the time she was appointed.

"There has been a witch-hunt against her. This witch-hunt has involved all the main parties in the House."