Australian Prime Minister Malcolm Turnbull has said he wants to sign a free trade agreement with the UK "as soon as possible" after Britain's withdrawal from the European Union and claimed he will not "muck about" getting it done.

Speaking at a joint press conference with Theresa May in Downing Street Mr Turnbull said his Government;s approach is "very simple" and wants to sign an agreement as soon as the UK is legally able to do so.

The EU has stipulated that Mrs May cannot sign new deals with other nations until Brexit talks have concluded.

In a good-humoured exchange Mr Turnbull said: "As Britain moves to completing its exit from the EU, we stand ready to enter into a free trade agreement with the UK as soon as the UK is able to do so.