Reality Check: How good a deal could UK do with the EU?
The Treasury says: "If EU countries were to offer the UK significant access to the Single Market, they would certainly insist that the UK accepts the associated obligations and rules, as every other country has had to do."
Norway and Switzerland, the two countries outside the EU with the closest relationship to it, are both obliged to make a financial contribution to the EU budget.
They also have to accept free movement and either comply with EU legislation or co-ordinate their own laws with it. Would it be the same for the UK? Some of the supporters of Leave claim not.
At the Treasury Select Committee last month, Boris Johnson suggested the UK could get a better deal. "Both of those would be locked off - free movement and budgetary contributions - but it would be massively in the interests of our partners to do a deal based on free trade in goods and services, and I am sure that is what we would achieve."
John Redwood said on BBC Radio 4's Today that he'd spoken to the German government who had made it clear they didn't want any new barriers to trade.
But that's hard to square with what politicians from other member states have said in public.
President Hollande of France has said "there will be consequences if the UK quits the EU… in many areas: the single market, financial trade, economic development between our two countries."
That point has been reinforced by the French Finance Minister Emmanuel Macron, who suggested that banks might leave Britain because they'd no longer have access to the EU's financial passport, which allows them to trade across the EU.
And German Finance Minister Wolfgang Schaeuble has said that Brexit would be followed by "years of the most difficult negotiations".
Reality Check verdict: We'd certainly be able to negotiate access to EU markets after Brexit, but it's hard to see other EU countries giving the UK a much better deal than everyone else.
READ MORE: The facts behind claims in the EU debate