An Australian-style points-based immigration is not a"silver bullet" to lowering net migration, the Prime Minister has said.

During the EU referendum a points-based system was lauded by Leave campaigners - such as the foreign secretary Boris Johnson - as an alternative migration system to the EU's free movement of people.

Theresa May, who supported remaining in the EU, criticised the system at a press conference with journalists in China where she is attending the G20 meeting.

The Prime Minister said: "You really don't want to ask a former home secretary about the intricacies of points-based systems. It might take a very long time answering your question.

"One of the issues is whether or not points-based systems do work, and so forth. "What I say is the voice of the British people was very clear. They wanted control in the issue of the movement of people coming in from the European Union.

"They didn't want free movement to continue as it has done in the past. We will be going out there to deliver on that."

She added: "A lot of people talk about the points-based system as always being the answer in immigration.

"There is no single silver bullet that is the answer in terms of dealing with immigration.

"You have to look across the board, you have to look at the whole range of issues, not just how you bring control through the rules we have for people coming in but also making sure you are rooting out abuse in the system and obviously dealing with people if they are discovered here illegally."

During the referendum campaign, Vote Leave campaigners proposed devolving aspects of the immigration system to Holyrood.

Liberal Democrats leader Tim Farron described the UK Government's stance on what happens after Brexit as a "farce".

Farron said: "The Prime Minister has now questioned the idea of a points-based immigration system so my question for the Brexiteers like Fox, Boris and Davis is this - what are you going to do now?

"Are you going to fight for the points-based immigration system you so vigorously proposed? Or are you happy to sit round the Cabinet table, with your red boxes and chauffeur-driven cars, and look the other way?

"This is the problem with the constant 'Brexit means Brexit' mantra - no one has any real idea about what the government is going to do, not even the Cabinet. It's a farce."

A spokesperson for the Prime Minister said a points-based system is "not an option" for Britain after leaving the EU.

The spokesperson said: "One of the opportunities of Brexit is that we will be able to control the number of people coming to Britain from the EU.

"The precise way in which the Government will control the movement of EU nationals to Britain after Brexit is yet to be determined.

"However, as the PM has said many times in the past, a points-based system will not work and is not an option.

"When Labour introduced a points-based system the numbers went straight up. In Australia, they have a points-based system and they have higher immigration per capita than Britain.

"A points-based system would give foreign nationals the right to come to Britain if they meet certain criteria: an immigration system that works for Britain would ensure that the right to decide who comes to the country resides with the government."