'Ram home the message' by enshrining an EU referendum in law to fight off Ukip, Boris tells Dave Stuart Wheeler (Rii Schroer for the Telegraph) Ukip treasurer Stuart Wheeler suggested that the party which was fielding 1,700 candidates would make net gains of 40 seats. The strong showing is expected to serve as a springboard for Ukip into next year's 2014 European elections, and the expected 2015 general election. In an interview with The Telegraph, Mr Wheeler suggested Ukip could win as many as 10 MPs in 2015, and help to form a Coalition in the event of a hung Parliament. Mr Wheeler compared the rise of Ukip to the increase in popularity in Scotland of the Scottish National Party. He said: "It really is difficult because the Scottish Nats came from virtually nowhere to have a majority in the Scottish Parliament. We could suddenly jump like anything. We may get none, or we could get a few or we could get a lot. Everyone would be very surprised if we got more than 10 [MPs] but you just can't rule out us getting much more than that even. Asked if Ukip could be in Government after 2015, he said: "If we did a deal it is not impossible we would have a minister or two." Mr Cameron suggested on Wednesday that he will bring in laws on a referendum before the end of this parliament in the hope of winning back voters from Ukip. Mr Johnson gave his support to the idea of early legislation, amid Tory fears that Ukip are stealing their traditional support over issues such as Europe and immigration. Are you in favour of Cameron bringing forward legislation for an EU referendum? However, Mr Johnson could not resist reminding his audience of Mr Cameron's 2009 about-turn on his "cast-iron" promise to hold a referendum on the Lisbon Treaty, which critics say effectively enacted the EU's draft constitution. He said: "It's very important that there should be clarity in people's minds, that we don't have a repeat of the situation we had with the Lisbon Treaty where we thought we were going to get a referendum and then it was somehow whisked off the table. So I'm sure the Prime Minister and the Government are absolutely sincere in their pledge to have a referendum, it's going to happen, but maybe just to ram that message home, some legislation would be a good idea. Mr Johnson's hopes of succeeding Mr Cameron as Conservative leader received a boost from Zac Goldsmith, the Richmond MP. In an interview with London's Evening Standard newspaper, Mr Goldsmith said many simply did not believe Mr Cameron's pledge of an EU referendum after the 2015 election. He said: "Whatever that magic dust is that politicians dream of, Boris has got it."