In an election campaign, politicians are known for going to great lengths in an attempt to secure your vote.

Eastern Daily Press: The first page of Theresa May's letter to Labour candidate Jo Rust. Photo: Jo Rust.The first page of Theresa May's letter to Labour candidate Jo Rust. Photo: Jo Rust. (Image: Jo Rust.)

But prime minister Theresa May has now taken the bold and surprising step of writing a letter to a Norfolk Labour parliamentary candidate – to try and persuade her to vote Conservative.

Even though she has been a well-known Labour activist and Conservative opponent for several years, Jo Rust – who is contesting the North West Norfolk seat – received the letter on paper headed 'Rt Hon Theresa May' on Tuesday, May 16.

Undeterred by Mrs Rust's clear support for Labour, the Conservative leader compares a 'coalition of chaos with Jeremy Corbyn' to the 'strong and stable leadership' offered by Mrs May and Sir Henry Bellingham, Mrs Rust's election opponent.

She then makes the surprising attempt to convert Mrs Rust with an appeal to 'back me by voting for my candidate, Henry Bellingham, in your local constituency of North West Norfolk'.

Eastern Daily Press: Jo Rust, who will stand for Labour in North West Norfolk. Picture: Matthew Usher.Jo Rust, who will stand for Labour in North West Norfolk. Picture: Matthew Usher. (Image: � ARCHANT NORFOLK 2016)

The Conservatives defended sending the letter, which was sent to all registered postal voters, saying there is a genuine desire for information about the candidates who are standing and that it is the party's policy to try and communicate as widely as possible.

Some Conservative members in North West Norfolk even claim to have had literature asking them to donate to the Labour party.

After outlining her views that 'this is a unique and crucial election for our country' and that 'making Brexit a success is central to our national interest', Mrs May goes onto describe Mrs Rust's party as a 'shambles' in the letter.

The letter, addressed to Mrs Rust's home, warns of what the PM believes are the risks of a 'vote for anyone but my candidate – Henry Bellingham'.

Eastern Daily Press: Prime Minister Theresa May during a visit to the International Aviation Academy in Norwich. Picture: Nick ButcherPrime Minister Theresa May during a visit to the International Aviation Academy in Norwich. Picture: Nick Butcher (Image: Archant � 2017)

Mrs May has another go at persuading Mrs Rust, saying: 'Give me and Henry Bellingham your support and I will get the best Brexit deal for you. I will stand up and govern for you.'

Perhaps unsurprisingly, Mrs Rust was not won over by the prime minister's appeal and will continue to campaign against her in the general election on June 8.

'Theresa May has really shown what a shambles any government led by her will be,' said Mrs Rust, who also stood in North West Norfolk in 2015, where she came second to Sir Henry.

'She refers over and over again to 'strong and stable'. I can't hear that now without imagining a darlek voice. She's not so strong and stable if she's addressing a letter to me, about me.'

Ian Sherwood, Conservative party agent for North West Norfolk, said: 'I am sorry Mrs Rust has taken offence by this' - but added: 'We'll continue to work hard to communicate with all electors.

'In fact, we've had a number of calls where people have said they agree with Theresa May and Henry Bellingham and will be supporting him in the election.'

And he critcised other parties, saying: 'I haven't had any communication from any other party.'

Sir Henry is defending a 13,948 majority in North West Norfolk.

As well as Mrs Rust, his opponent are Andrew De Whalley for the Green Party, Rupert Moss-Eccardt for the Liberal Democrats and Michael Stone for the UK Independence Party.