Sir Roger Douglas is hanging up his parliamentary hat at the end of the term in November, but not before firing a few parting shots at the Government and a lament for the old days.

"I have to think about the fact that I will be 77 at the end of next term if I stayed on," Sir Roger said.

"I'm looking forward to watching my grandson play cricket, things like that."

Sir Roger first entered Parliament in 1969, became renowned for the economic reforms of the 1980s that became known as Rogernomics, and left in 1990, only to return this term on the Act Party list.

"Have I enjoyed the last three years? Clearly the answer to that is 'yes' and 'no'. I sit on the sideline, I believe I know what should be done, and that can be terribly frustrating.

"You give the odd speech and write the odd article, but that's about the limit of what you can do."

He said Prime Minister John Key had more political credits than anyone he had known in politics, "but he won't spend any".

"One day he'll find all his credits are dead. And you can't deliver unless you have policies that work, and we don't. The only thing he has going for him is that the other lot would be much worse."

He acknowledged it had been a tumultuous term for Act, including David Garrett's resignation, the rolling of Heather Roy as deputy leader, and Sir Roger and Act leader Rodney Hide being accused of bad judgment in using the now-axed international airfare subsidy.

"One or two cases, including my own, we brought it on ourselves ... I handled that badly. Rodney handled his expenses badly."

He lamented the camaraderie of the old days. "There was more of the club atmosphere. Government and Opposition members used to have breakfast together. We went to the bar.

"Now I'm sometimes the sole MP in there. They're scared that the journalists will be up there and someone will say something out of line."

When asked about regrets, he said: "I would have liked to have done a lot more in terms of social policy, the agenda we started in the 1980s carried through to health, education and welfare. There are regrets, but that's life.

"I've just had enough of having to be in the House until 9pm."