Dorries was born as Nadine Vanessa Bargery in Liverpool. Her father was a bus driver who became a lift operator having suffered from Raynaud's disease, which had necessitated the amputation of his toes. Her father was a Roman Catholic of Irish descent, while her mother was an English Protestant. Dorries was raised as a Protestant.

She was reportedly part of a plot to oust John Bercow from the Speaker's chair in the run up to the 2010 general election, and, after the election, sent an email to all new MPs advocating his removal. Writing in the Daily Mail, just before his tenure was reapproved, she objected to Bercow's abandonment of the speaker's "magnificent" ceremonial clothes and placed herself among those MPs who accuse him of not carrying forward "the great tradition of authority, control and impartiality".  On 9 May 2010, two days after retaining the Mid-Bedfordshire seat at the general election, The Sunday Times revealed that Dorries was facing the first complaint about an MP's expenses claim of the new parliament. The newspaper reported that she had claimed around PS10,000 for an annual report in 2007 on her performance as an MP, but that her former Commons researcher had never seen the report or worked on it. Dorries insisted that she had indeed published the report, placing a photograph of it on her blog. She subsequently told the Biggleswade Advertiser that the report was never printed and a credit note issued with refund on 13 September 2008.  On 13 January 2011, it was announced by the Daily Mirror that police were investigating Dorries concerning her expenses. Three days later, The Sunday Times reported that police had since handed a file to the Crown Prosecution Service for consideration. In February 2013, it was reported that Dorries was being investigated by the Independent Parliamentary Standards Authority over her expenses, although no specific details were given at this time.  On 27 June 2013, Dorries announced she would no longer claim her personal expenses as an MP, but would draw on her salary for such costs. She argued that she would be in a better position to campaign for the abolition of the present expenses arrangements by doing so. Dorries herself stood for election as a deputy speaker after one of the three posts became vacant. In the Commons vote during October 2013, she gained the support of 13 MPs, and was the first of the six candidates to be eliminated in the voting process.

What was the result of that investigation?
On 27 June 2013, Dorries announced she would no longer claim her personal expenses as an MP, but would draw on her salary for such costs.