These are the official numbers.
https://www.electoralcommission.org.uk/who-we-are-and-what-we-do/elections-and-referendums/past-elections-and-referendums/eu-referendum/campaign-spending-eu-referendum
Remain: £19,309,588
Leave: £13,332,569
When the extra £9 million of tax payers money that the Gov spent on sending their 'advice' to all UK households to recommend remaining in the EU is added, then it can be seen that more than double the amount was spent on the remain effort than on the leave campaign.