UPDATED 2.14pm: Bill English now has the numbers to become Prime Minister, based on public declarations.

LISTEN ABOVE: Newstalk ZB Political Editor Barry Soper speaks to Kerre and Mark Afternoons

At least 30 MPs have committed to backing English, meaning he has half of the votes of National's 59-vote caucus.

Judith Collins has also withdrawn her bid for the leadership, and thrown her support behind Bill English.

English stated earlier today that he would appoint senior Minister Steven Joyce as his Minister of Finance if he wins, which now looks certain.

Neither of the other candidates, Jonathan Coleman and Judith Collins, have so far received any public declarations of support.

Coleman has indicated that he will not yet withdraw.

He said he has not seen the numbers or heard from Bill English.

Mr Coleman said it's outside speculation that Mr English has the numbers and he will decide later.

Backbenchers Paul Foster-Bell, Jami-Lee Ross, Brett Hudson, Chris Bishop and Jo Hayes are among those who have thrown their support behind English.

Todd Muller announced on Thursday he would back English as leader and Transport Minister Simon Bridges as deputy over Social Housing Minister Paua Bennett.

Amy Adams has reportedly declared her support for Bennett as deputy. 

A vote will be held next Monday.

The National MPs who have ​declared their support for English: 

Bill English

Nikki Kaye

Anne Tolley

Louise Upston

Michael Woodhouse

Hekia Parata

Nathan Guy

John Key

Nuk Korako

Nick Smith

Chester Borrows

Murray McCully

Simon Bridges

Paula Bennett

Paul Foster-Bell

Jacqui Dean

Brett Hudson

Jonathan Young

Jami-Lee Ross

Todd Muller

Chris Bishop

Amy Adams

Mark Mitchell

Alfred Ngaro

Barbara Kuriger

Jono Naylor

Todd Barclay

Chris Finlayson

Joanna Hayes

Steven Joyce