Arron Banks anger at Peter Bone and Tom Pursglove payments
Two Tory MPs have come under fire for paying themselves a total of £40,000 for running a not-for-profit campaign for a Leave vote in the EU referendum.
Donor Arron Banks said he was "extremely shocked and disappointed" that Peter Bone and Tom Pursglove had profited from Grassroots Out.
He called on them to pay the money to a "smaller Brexit" campaign.
But in a joint statement, the MPs said employing them was "clearly the most cost-effective way" of campaigning.
The payments were revealed in the register of members' interests.
Grassroots Out was founded in December by Mr Bone and Mr Pursglove, with backing from UKIP leader Nigel Farage and, later, Labour MP Kate Hoey.
'Business not a cause'
It came close to being designated the official Leave campaign by the Electoral Commission, but lost out to Vote Leave.
Mr Bone's accountancy firm PWB received a total of £21,750 from Grassroots Out in the first four months of this year, according to his entry in the register of members' interests.
That was made up of two payments for accountancy services, of £17,500 and £2,500, at a rate of £42 an hour, and a £1,750 director's fee.
Mr Pursglove charged Grassroots Out a total of £19,250 - £17,500 for 450 hours' work as chief executive - between 16 December and 31 March - and £1,750 in director's fees, according to his entry.
In a statement, Arron Banks, who says he has given £4m of his own money to his Leave.EU campaign, a group which also funded Grassroots Out, criticised the pair.
The statement said: "Leave.EU has raised £9m to fight the Brexit cause, £5m personally from Arron Banks, £4m from other donations including over 5,000 individuals.
"We are extremely shocked and disappointed to discover that two elected individuals have treated the GO Brexit campaign as a business, not a cause, and would urge them to do the honourable thing and donate the sum directly to a smaller Brexit group."
'No financial gain'
But the MPs said some individuals "had jumped to conclusions without being in full possession of the facts".
"Of all the major EU referendum campaigns, we have the cheapest and most efficient structure in place and our administrative and running costs are by far the lowest," they said.
Using the two MPs had allowed Grassroots Out to "keep costs to a minimum, allowing us to spend the maximum amount on campaigning", rather than hiring outside expertise, they added.
They said they had "properly" made the declaration in the Register of Members' Interests adding: "It must also be clarified that both Peter Bone MP and Tom Pursglove MP have made donations to Grassroots Out Ltd that exceed the level of the payments received.
"These donations will be listed in the official return made to the Electoral Commission. Neither Peter Bone MP, or Tom Pursglove MP, have made any financial gain from this arrangement."