It wasn't that big a story in December 2006 when a fairly low profile Antrim councillor voiced reservations about gay couples staying in his bed and breakfast.

But now those comments by Ulster Unionist Adrian Watson are causing problems for his party's electoral link-up with David Cameron's Conservatives.

That pact has just this week cost the UUP its sole MP, with Lady Hermon declining to defend her North Down seat under the Conservative banner. Now the Watson saga is posing another headache that the two parties could do without.

The councillor is the UUP's choice to run in the South Antrim constituency in the General Election.

The seat, held by veteran DUP MP William McCrea, must be close to the top of the Ulster Unionist hitlist. But Mr Watson is not guaranteed the nomination, as it has to be ratified under joint Conservative-UUP procedures.

There has been ongoing speculation about opposition to him in Tory ranks.

The fact that his three-year-old comments are back in the headlines also says something about changing attitudes in politics.

In truth, there will be many rank-and-file members of the Conservative Party who would echo Mr Watson's remarks on homosexuality, and have a lot more to say besides. But for the Cameron leadership, such views would be regarded as poisonous.

One of his chief aims has been to ‘detoxify’ his party's brand.

”If we do win the next election, instead of being a white middle-class middle-aged party, we will be far more diverse,” he said last year.

This is not just about Cameron making it clear that gay voters are more than welcome. The wider tactic has been to present today's Tories as more liberal and less censorious than their old-style predecessors.

It can be argued that attitudes have been changing in Northern Ireland too. There was an outcry when Ian Paisley jnr spoke in 2007 about being “repulsed” by homosexuality. However, that controversy was nothing compared to the storm that broke out a year later when Iris Robinson made her infamous “abomination” remarks about homosexuals.

The DUP's record on gay rights was cited in recent weeks when there was talk of a unionist unity pact with the Ulster Unionists.

A Tory source was keen to quash suggestions that it would be on board for such a tie-up, telling this newspaper: “David Cameron has not spent four years dragging our party into the 21st century for us to do a deal with the DUP.”

It is clear that an association with the DUP would have been used against the Conservatives in Britain, in a bid to undermine their new image.

Having Adrian Watson as one of their candidates could pose a similar risk.