UKIP Leader Nigel Farage: "I congratulate Vote Leave on getting designation.
"The decision of UKIP to back Grassroots Out was on the basis that they saw the importance of the immigration issue in this referendum, and that we wanted to reach out across the country at a grassroots level and work with everyone from the left, centre and right of British politics to get our country out of the EU. I believe this approach is the only way the Leave side can win this referendum.
"It is clear that Vote Leave now share my view on this approach, for instance the issue of EU open borders is now a prominent part of their campaign messaging.
"Regardless of whichever campaign got the designation, UKIP would always have played a big role in this campaign as the only national party committed to leaving the EU and with a substantial £4 million spending limit.
"I have always wanted all on the Leave side to come together and have done my best to try and make this happen. I'll continue to do so in the run up to the referendum to ensure the Leave side wins.
"We in UKIP, as I've said from the start, will work with anyone that wants to leave the EU. We must work together to get our country out of the European Union."