The latest batch of unwanted headlines concern the constituency centre which the MLA and his First Minister father run in Ballymena.

Mr Sweeney obtained the mortgage for this property last summer, and was for a time sole director of the company - Sarcon (no 250) - that owns it.

But Mr Paisley Jnr has stressed that the businessman was only briefly connected to Sarcon (no 250) and resigned as a director before any rent was due.

He also stated that Mr Sweeney, one of north Antrim's top property tycoons, gave advice on the purchase of the office.

The latest link between the MLA and the developer comes after months of controversy over Mr Paisley Jnr's lobbying for Mr Sweeney on issues such as his Giant's Causeway visitor centre plan and a proposed purchase of prime publicly-owned land at Ballee, Ballymena.

Confirmation of the office arrangement came in a statement by Mr Paisley Jnr, reported by this newspaper on Saturday.

He said: "I can confirm that a company called Sarcon 250 owns the DUP office at 9-11 Church Street and has done since the summer of 2007.

"During the run-up to the purchase, for a period of weeks, Mr Sweeney, as a member of the DUP, gave advice on the purchase of the office and became a director of the company to ensure that the purchase could be completed.

"He subsequently resigned before any rent was due under the lease, in favour of a new director, as it was never intended that he would have any further role or be in receipt of any benefit."

MLAs receive rental expenses for their constituency offices from the Assembly.

A DUP Stormont source last night told the Belfast Telegraph: "People in the party are just sick to the back teeth of all this. His problems are even being partly blamed for the loss of the by-election in Dromore last week."

Mr Paisley Jnr and his supporters continue to state that he has done nothing wrong.

It is also argued that it is entirely right for a politician to speak up for a prominent businessman in his constituency.

However, critics are certain to seize on the constituency office revelations, and will again attack the junior Minister and his party on the Sweeney connection.

It will be argued that the developer was providing free advice and facilitating a mortgage for the office, just weeks after Mr Paisley Jnr had lobbied Social Development Minister Margaret Ritchie on the asking-price for the publicly-owned Ballee land.

The mortgage deal was also finalised less than two months before the furore surrounding Mr Sweeney's planning application for a Giant's Causeway visitor centre development - when the MLA famously said "I know of him" about the businessman.