Philip Hammond, last week appointed as foreign secretary, has confirmed that he would vote for Britain to leave the European Union unless there was significant reform in Brussels.

In an interview on the BBC's Andrew Marr show on Sunday, Hammond said that current arrangements were "simply not acceptable" and that he stood by the answer he gave in an interview a year ago when he said, if he had to choose now, he would vote for withdrawal from the EU.

David Cameron is committed to renegotiating Britain's relationship with the EU and then holding an in/out referendum before the end of 2017 but he and William Hague, Hammond's predecessor, have always refused to acknowledge that they could vote no, arguing it is defeatist to go into negotiations contemplating defeat.

But Hammond chose not to equivocate in one of his first interviews since his appointment on Tuesday. Asked if he would still prefer to leave the EU rather than accept the status quo, he replied: "I haven't changed my mind.

"If there is no change at all in the way Europe is governed, no change in the balance of competences between the nation states and the European Union, no resolution of the challenge of how the eurozone can succeed and co-exist with the non-eurozone, that is not a Europe that can work for Britain in the future. So there must be change, there must be renegotiation."

Hammond said he accepted that "Britain gains enormously from being inside the European single market", but added that overall the status quo was "not in Britain's interest".

"What I can tell, and have told my European colleagues, is that if the offer by European partners is nothing, no change, no negotiation, I am pretty clear what the answer of the British people in that referendum is going to be. There has to be substantive renegotiation that addresses the concerns that Britain has."

Asked what his priorities would be in renegotiation, Hammond replied: "There has to be a repatriation of powers to the nation states, a recognition – and this is not just a British demand, it's a demand from other countries too – that what can be done at national level should be done at national level.

"We should only do things at European level where it is absolutely necessary to do them at European level."

Hammond said it was also important to settle the relationship between states in the eurozone and those outside "in a way that is fair to the non-eurozone and protects its interests".

In a separate interview, Dominic Grieve said it was "certainly possible" that he was sacked in the reshuffle from his post as attorney general because he was opposed to Britain leaving the European convention on human rights – an idea that Cameron is considering.

Grieve said that, as well as having "reputational consequences", leaving the convention while remaining in the EU could lead to the European court of justice stepping in to enforce convention "norms" on the UK.

"And unlike the [European court of human rights] in Strasbourg, where a judgment is just an international obligation, [an ECJ ruling] has direct effect and has to be applied here," he said.