But former Treasury adviser Sir Alan Budd said he was unable to prove if Mr Blunkett had instructed Leoncia Casalme’s case to be “fast-tracked”, or if he raised it as an example of poor performance in his Immigration and Nationality Directorate (IND).
The Conservatives described the inconclusive outcome of the inquiry as “an open verdict”.
Downing Street said Tony Blair held firm to his view that Mr Blunkett left the Government with his integrity intact, interpreted by many at Westminster as leaving the door open for him to return to the Cabinet after the forthcoming general election.
The Budd Report came an hour after a report by the Parliamentary Standards Commissioner Sir Philip Mawer, who found Mr Blunkett breached Commons rules by giving his former lover Kimberly Quinn a rail warrant worth £179 (€258). Parliamentary rules state the rail passes may be used only by MPs’ spouses.
Mr Blunkett yesterday said he had apologised “unreservedly” for what he said was “a genuine mistake”.
In his report, Mr Budd made clear he did not believe there had been any effort to stage a “cover-up”.
The inquiry followed allegations Mr Blunkett “fast-tracked” Ms Casalme’s application as a favour to Mrs Quinn.
The key piece of evidence was an email exchange uncovered by telephone, fax and email records.
On May 8 last year, Mr Blunkett’s private secretary for immigration messaged the private secretary of IND director general Bill Jeffrey, asking if there was any update on “the case I faxed through to you the other day”.
The following day, a response came: “Sorted - she has been granted ILR (Indefinite Leave to Remain) - papers will be sent to her shortly. The case was in ICU (Initial Consideration Unit), so they pulled it out of the queue and made a decision - (no special favours, only what they would normally do - but a bit quicker).”
No trace was found of the fax.