Sir Stephen Bubb has warned the government that charities may boycott the Giving Summit this year over the recently-announced tax allowance cap on donations.

The Giving Summit was initially planned for last autumn, having been announced in the government's white paper on giving, but was rescheduled and is now due to take place in May at the Natural History Museum. The Prime Minister is among those due to attend.

But Sir Stephen told the Financial Times that controversial plans announced in last week’s Budget that mean donors will be limited to claiming tax reliefs of the greater of £50,000 or 25 per cent of their total income, cannot be supported by the sector's leaders:

“It is hard for charity leaders to sit quietly listening to plans to get people to give more when their fundraising strategies have been torpedoed. There is a simple solution: remove charity donations from the proposed new tax allowance cap. Do it before damage is done."

The Budget plan sparked an immediate backlash from charities and philanthropists alike, who cautioned that this could lead to a fall in large donations.

Major donor and financier John Spiers claimed the new tax cap will limit the amount he is now willing to give: “I give the majority of my income away. If this goes through as planned, it will reduce my philanthropic activities very substantially. The relief was not of any benefit to me, but it means money going to good organisations that deliver a good return will instead go to the government," he said.

With average earners less able to donate during the current economic conditions, charities have been targeting wealthier donors to fund campaigns.