Sainsbury joined the Labour Party in the 1960s, but was one of the 100 signatories of the '
Limehouse Declaration' in an advertisement in
The Guardian on 5 February 1981; he went on to be a member of the
Social Democratic Party (SDP) formed by the authors of the Declaration. Following the
1983 election, he prompted the party to give more priority to recruiting members and finding a firm financial base; he was by far the biggest donor to the party, and a trustee, giving about £750,000 between 1981 and 1987. His donations were typically earmarked to specific projects rather than general day-to-day operations. Along with
David Owen, Sainsbury opposed merging the SDP with the Liberal Party following the 1987 election, and provided office space for Owen to help him re-establish a separate political party, which was created in 1988. The
'continuing' SDP was wound up in 1990, and Sainsbury changed allegiance back to the Labour Party, rejoining them in 1996. A year later, following the Labour Party's election victory, he entered the
House of Lords as a Labour peer, being created Baron Sainsbury of Turville,
of Turville in the County of Buckinghamshire, on 3 October 1997. Between 1996, the year he rejoined Labour, and 2006, when he stood down as a government minister, Sainsbury donated £16 million to the Labour Party, usually in batches of £1 million or £2 million each year. He donated a further £2 million on 7 September 2007, stating that he was impressed by Gordon Brown's leadership and believed "that Labour is the only party which is committed to delivering both social justice and economic prosperity". He gave another £500,000 on 15 December 2008, making a total of £18.5 million. He is associated with the
Labour Friends of Israel. In April 2006, it was reported Sainsbury "faced a possible probe into an alleged breach of the ministerial code after admitting he had failed to disclose a £2 million loan he had made to the Labour Party – despite publicly stating that he had." He subsequently apologised for "unintentionally" misleading the public, blaming a mix-up between the £2 million loan and a £2 million donation he had made earlier. In July 2006, he became the first government minister to be questioned by police in the "
Cash for Peerages" inquiry. On 10 November 2006, he resigned as Science Minister, stating that he wanted to focus on business and charity work. He categorically denied that his resignation had anything to do with the "Cash for Peerages" affair, although this was contradicted by subsequent press reports attributed to "Labour insiders" which suggested that his resignation was indeed a direct consequence of the affair. From July 1998 to November 2006, he held the office of
Parliamentary Under-Secretary of State for Science and Innovation at the
Department of Trade and Industry, serving in the
House of Lords and accepting no salary. Because of his importance to the Labour Party as a donor, contemporary press reports described him as "unsackable". He has argued that there are "far too many
reshuffles", and that there were considerable benefits to his remaining in post for so long. Sainsbury has also been associated with the
Institute for Public Policy Research and
Progress. Between 2001 and 2011 he provided £2 million of funding for Progress. In 2009, he created the
Institute for Government with £15 million of funding through the
Gatsby Charitable Foundation to help government and opposition politicians to prepare for political transitions and government. He donated £390,000 to Progress and the Movement for Change between December 2011 and April 2013, while he was not on a UK electoral register, which is contrary to
electoral law, leading to Progress and the Movement for Change being fined by the
Electoral Commission. Sainsbury funded the "Remain" side of the
2016 European Union membership referendum campaign, giving £2,150,000 to the Labour and £2,125,000 to the
Liberal Democrats "Remain" campaigns. After the
2017 general election, Sainsbury announced he would no longer provide financial backing to party political causes, but will donate to charitable causes. During 2016 he had donated £260,000 to
Progress in addition to backing "Remain" organisations. However, in late 2018 he donated £25,000 to Scottish Conservatives MP
Luke Graham. During the
2019 United Kingdom general election campaign Sainsbury donated £8 million to the
Liberal Democrats, over half the party's election funding, making its election donations larger than the Labour Party's. Sainsbury has been a long-time patron of the
socialist society Scientists for Labour. He ranked 14 out of 50 on the Top 50 Influential Lib Dems of 2020 list – the only non-Lib Dem member to feature. ==Charitable works==