ACT Party leader Rodney Hide advises Liberal Democrat leader Nick Clegg not to overreach in negotiations over the formation of a new government in Britain.
Thursday's general election resulted in the first hung parliament since 1974.
The Conservatives won the most seats in the election, but failed to secure an overall majority.
The New Zealand Cabinet Manual, a blueprint for how to form and run a government, is reportedly being used for guidance in resolving the hung parliament.
Mr Hide says it will be a bumpy road for Britain, which does not have recent experience of a multi-party government.
Mr Hide says Mr Clegg has never had so much power as he does right now.
But he says Mr Clegg must know his place in negotiations and remember that he only represents a minority.
ACT has a confidence and supply agreement to keep the National Party in power.
Mr Hide says no coalition agreement can cover every contingency and the most important aspect is an open relationship and a 'no surprises' policy.