A long-serving former Harrods executive has claimed that his offer to become boss of the department store chain Fenwick was withdrawn because of his time working under Mohamed Al Fayed.

Al Fayed, who owned the luxury London store for more than two decades, has been accused of sexual assault or rape by more than 20 women following a BBC investigation.

Nigel Blow, who worked for 14 years at Al Fayed’s companies, said he “never heard about or witnessed” grooming, sexual assaults or rape.

He said he had been deemed “guilty by association” by Fenwick. Fenwick declined to comment.

“I worked at Harrods in senior roles from 2002 to 2007. I can confirm that, during my time at the business, I never heard about or witnessed any such behaviour by Mr Al Fayed.”

“I believe Fenwick’s action is unjustified, unfair and in breach of contract,” Mr Blow told the BBC.

Mr Blow also criticised the BBC over its reporting of executives who had worked with Al Fayed.

“It would appear that the BBC team is prepared to tarnish or ruin the reputation of every senior person who worked at Harrods during Mr Al Fayed’s ownership, under the serious and damaging misapprehension that of course they must have known.”

A BBC spokesperson said: “We stand fully behind our journalist and our journalism. This story, which was fully in the public interest, was produced in line with the BBC’s editorial standards, including contacting Mr Blow before publication.”

On Tuesday, Fenwick told the BBC that Nigel Blow had said he would no longer be taking up the position as their chief executive later this month.

No reason for the decision was given.

Mr Blow’s statement on Friday said that the Fenwick chair Sian Westerman told him it was not able to proceed with the employment “in order to safeguard the reputation of the Fenwick business.”

Fenwick declined to comment on this claim. The retailer, which is best known for its 140-year-old store in Newcastle, has eight stores around the UK.

Mr Blow joined Harrods in 1992.

There were several reports of Al Fayed’s alleged abuse of women in the following years including a profile in Vanity Fair alleging sexual misconduct against staff, an ITV documentary and a book detailing alleged sexual assaults.

Mr Blow said that Harrods staff had their offices, phones and cars bugged, and at one point he was followed by the Harrods security team.

“On multiple occasions I saw transcripts of my own telephone calls on Mr Al Fayed’s desk. Such behaviour prompted me to seek alternative employment from 2006,” he said.

In 1997 the Observer published detailed allegations of bugging of Harrods executives and staff carried out on Al Fayed’s orders – and the ITV documentary played excerpts from the tapes.

Mr Blow is currently chief executive of the department store chain Morley’s, based in Wimbledon, though he resigned the position to take up the new job.