1st term as MP (2015–2017)
At the 2015 general election, Mann was elected to Parliament as MP for North Cornwall with 45% of the vote and a majority of 6,621. Along with Sarah Newton, MP for Truro & Falmouth, he took his Parliamentary oath in the Cornish language.
In November 2015, Mann introduced a Private member's bill to give Town and Parish Councils the power to hold community referendums to alter speed limits. The Bill received its second reading in February 2016, but as it was opposed by both the Government and the Opposition, it was subsequently withdrawn.
Following his election as an MP he resigned as a councillor in February 2016, after he had come under pressure to resign for his poor attendance at council meetings.
In May 2016, it emerged that Mann was one of a number of Conservative MPs being investigated by police in the 2015 United Kingdom general election party spending investigation, for allegedly spending more than the legal limit on constituency election campaign expenses. However, in May 2017, the Crown Prosecution Service said that while there was evidence of inaccurate spending returns, it did not "meet the test" for further action.
Mann campaigned for the United Kingdom to leave the European Union in the 2016 EU referendum.
In December 2016, Mann was elected unopposed to the House of Commons' Environmental Audit Select Committee, on which he served until May 2017.
In March 2017, The Daily Telegraph reported that Mann was one of nine MPs who had claimed Amazon Prime subscriptions on their parliamentary expenses. The Independent Parliamentary Standards Authority, responsible for handling expenses claims, told the paper subscriptions could be claimed but MPs must "justify the subscription is primarily used for Parliamentary purposes". He responded that the subscription was a mistake after his office had purchased stationery from the website, and that Amazon had issued a refund.
