All four were referred to the Standards Board for England, in the wake of allegations surrounding the so-called "tainted cash" row.

Complaints were made last October against Tory councillors Ian Fowler, Tony Lee, Jim Houlds-worth and Ron Bell.

The first three have been cleared of committing any breaches in relation to their duties as councillors, while the outcome of the investigation into Coun Ron Bell has not yet been completed.

A £10,000 donation by housebuilder Kensington Developments to the Blackpool South Conservative Association sparked controversy because the company was asking for planning permission to build hundreds of new homes on Marton Moss.

It was claimed councillors Fowler and Lee must have known about the £10,000 donation and so were wrong to sign a letter saying they knew nothing about the gift.

The complaint against Coun Houldsworth claimed that, as a member of the council's development control committee, he should have declared an interest because he must have known about the donation.

The Standards Board ruled Coun Houldsworth did not have a personal interest in the Kensington donation and so "the donations do not amount to an interest that Coun Houldsworth was required to register."

The reports relating to Coun Fowler and Coun Lee say that in signing the letter, they were "not acting as a councillor" and therefore are not covered by the code of conduct.

In both cases, the report adds: "Therefore, whether or not he knew of the donations is not an issue about which she (the investigating officer) needs to form a view."

A spokesman for the Standards Committee said the investigation into Coun Ron Bell was still ongoing.

Coun Houldsworth hinted the Conservative party was still divided over the decision of 21 councillors to sign the letter.

He said: "I'm very happy that everyone who did not sign the letter has been found not to have done anything wrong.

"I look forward to moving on."