Gordon Brown's government did reward the Democratic Unionists for backing the 42-day detention of terror suspects, Northern Ireland's first minister claimed today .

In his new year message, DUP leader Peter Robinson said his party's decision to support the 42-days bill helped deliver major economic investment for the province.

But Robinson repeated an earlier denial that his party had sought or been granted political favours for backing the prime minister before the crucial Westminster vote on the issue in June.

Robinson said the decision had proved the DUP was a responsible party and that the government later "bent over backwards to help" it.

The House of Commons split by 315 votes to 306 over the controversial counter-terrorism bill – with the DUP's nine MPs securing a crucial victory for the government. The bill was defeated in the House of Lords in October.

Brown denied his government had bought the DUP votes and today Robinson said his party had simply done the right thing.

"It would have been much easier to vote with the Conservative party than to vote with the government," he said.

"We did what was right. And I think we showed at the same time that our votes matter at Westminster.

"We showed we are a party that can determine a major issue – perhaps the most major issue of the last year at Westminster."

He added: "We neither sought nor received any pay-off for that. But I think we have seen since then that if you act responsibly with government, government in turn will act responsibly with you."

In July it was announced that Bombardier Aerospace was investing half a billion pounds in Northern Ireland, sustaining more than 800 jobs at the Shorts aircraft factory in Robinson's East Belfast constituency.

"They [the government] came up with the goods in terms of the Bombardier deal ... which was the largest single investment in Northern Ireland," Robinson said. "But they bent over backwards to help us."

In November a £900m financial deal to kickstart Northern Ireland's devolved government was finalised after talks involving Brown.

Robinson said: "Would we have got the £900m if we had been irresponsible in the way that we behaved at Westminster? I think there is a recognition that if you are seen to be acting responsibly, then people will act responsibly with you."

He said the government had also brought forward legislation to compensate Orange Order halls attacked by arsonists and accepted DUP changes to the proposals.

The first minister added: "We didn't ask for any of those things. We recognised that if people saw that we were behaving responsibly, that we were a credible party at Westminster, that they could deal with, that people would deal with us in a way that was helpful to the electorate in Northern Ireland.

"But there is no link between the two – other than the fact that people knew that when we asked for something, we genuinely had a good reason for doing so."