“I am sorry that we failed to convince the British people,” wrote my friend and former Department of Trade and Industry colleague Lord Sainsbury as the Electoral Commission published details of his crucial donations towards trying to help Britain remain in the European Union. I feel his pain.

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Alongside funding for the main campaign – StrongerIn – the former science minister provided Labour and the Liberal Democrats with ringfenced funding to help us make the progressive case for remain to our supporters. It was welcome when offered, and critical to our efforts.

This contribution was not a secret. Anyone in the party who took an interest in the campaign would have known about it. The money helped us tour the country making the case for staying in the EU. Workers’ rights and environmental and consumer protections are not cheap values to defend. I, for one, am very grateful that Sainsbury helped our campaign. I know Tim Farron will feel the same.

What is surprising is that John McDonnell has decided to attack Labour’s biggest ever donor for the ringfenced £2.1m he gave to both the Liberal Democrats and Labour to aid the remain campaign. Yet Sainsbury has also given more than £20m to Labour over two decades – not just because he is generous, but also because, as science minister, he laid much of the groundwork for helping a vibrant research and development and manufacturing base continue in the United Kingdom.

It was this work that informed much of the “industrial activism” pioneered while Gordon Brown was prime minister, which received broad support across the party, including everyone from Peter Mandelson to the unions and the Labour left.

Lord Sainsbury's money helped us tour the country and make the case for staying in the EU

McDonnell’s attack is also surprising because Sainsbury’s book, Progressive Capitalism, is a clear retort to the neoliberalism that McDonnell himself rails against. Yet he now suggests that Sainsbury, for making his remain donation via the Liberal Democrats, could be suspended from the party. Labour’s shadow chancellor should be taking Sainsbury out to lunch to pick his brains, not turning to the media to pick fights.

Many people offered to give Labour money to help them communicate the pro-EU message to the party’s supporters. These donations should also be welcomed – especially by senior shadow cabinet members who demand from the party the resources necessary to get their views across. I notice McDonnell did not turn down any of the LabourIn support that was offered to aid visits and media appearances.

Sainsbury did not just help his party fight its corner – he put his country first and went the extra mile to keep Britain in Europe. If only everyone in Labour had done as much.