Labour’s planned holiday tax on British staycations will threaten its parliamentary majority, a new poll has shown. The tourist tax will allow mayoral authorities in England to impose a levy on the cost of an overnight stay in their areas – a policy that critics have claimed will be a “death knell” for British seaside resorts. New polling by the industry body UKHospitality has found that 56 per cent of Britons oppose the tax, which would add more than £100 to the cost of a two-week family holiday. The survey of more than 10,000 people also found that voters were nearly 10 times as likely to punish an MP who backs the policy than to reward them, at the ballot box. In 200 of the 411 seats Labour won at the last general election, the number of voters who said they would be less likely to support their MP because of the policy exceeded the party’s majority in that seat. The policy will allow mayoral authorities in England to impose a levy on the cost …