As election year rolls around our politicians are under increasing scrutiny – including over their physical appearance.

Labour leader Phil Goff returned this week from his summer break looking decidedly more youthful – but dodged questions about whether he has dyed his hair, as he tries to win the right to run the country.

Like his National counterpart, Prime Minister John Key, Mr Goff had been looking increasingly grey around the temples.

AFTER: A far less grey Phil Goff speaks yesterday.

But while Mr Goff refused to say whether he had begun to colour his hair, Mr Key insisted yesterday that hair dye had never touched his locks. `No. I constantly read about myself going grey and there's very little I can do about that," he said. "It's falling out but it's not changing colour."

Mr Goff waved off reporters, saying they shouldn't ask personal questions.

He is not the first politician to face scrutiny over his appearance in the run-up to an election – former prime minister Helen Clark faced questions over whether her billboards were air-brushed.

Massey University political marketing expert Claire Robinson said there was research that showed the more attractive a politician looked, the more support he or she could get from people who knew nothing about them.

Although Mr Goff had wide public exposure, he continued to suffer from a "wooden, stiff and grumpy" image. "I think most New Zealanders will recognise him, but they just won't necessarily know much more about him.

"It's not his hair colour that's the problem. It's the way he comes across. He tenses up when he's being interviewed. He comes across as being really angry, and Key comes across as being relaxed and casual and everybody loves him.

"It's really, really hard for Goff to cut through that, but hair dyeing is absolutely not going to make a jot of difference."