That's quite a claim. Do you have some strong evidence to back it up?
The electoral commission went to great lengths and expense to find any wrong doing and came up with nothing.
https://www.google.com/amp/s/www.telegraph.co.uk/politics/20...
Edit:
Rant alert:
It really irks me that the people who call the Brexit election unfair, don't seem to acknowledge that Britain was never given any kind of referendum when joining the EU
"Although the United Kingdom ratified the treaty in Parliament, this was not without some opposition. Broadly the governing Labour party supported the treaty, while the opposition Conservatives did not. The Liberal Democrats supported the treaty, while calling for a referendum on the UK's membership of the EU as a whole.[119] Several 'Eurosceptic' MPs called for a referendum on the ratification of the treaty. Daniel Hannan pointed out that the Prime Minister, Tony Blair had twice promised a referendum on the matter, to which Blair replied that he had promised a referendum on the European Constitution rather than the Lisbon Treaty, which unlike the former was not a constitutional treaty.[120] In early October 2007, the Commons' European Scrutiny Committee had found that the treaty was "substantially equivalent" to the rejected constitution.[121]"
https://en.wikipedia.org/wiki/Ratification_of_the_Treaty_of_...