Initially regarded as a right wing Thatcher loyalist, he privately told her her career was finished after she failed to win outright in the first round ballot of a leadership challenge, and subsequently urged her ultimate successor John Major to stand for election to succeed her.

[9] In 1992, John Major made Lilley the secretary of state at the Department of Social Security at a time when the number of claimants of sickness benefits was growing rapidly.

Spitting Image depicted him as a commandant at a Nazi concentration camp and commentator Mark Lawson of The Independent said that if Lilley stayed as Secretary of State for Social Security, it would be "equivalent to Mary Whitehouse becoming madam of a brothel".

He said, "They call it 'Land of Pseudo Tories' and it goes like this: "Land of chattering classes, no more pageantry / Darlings, raise your glasses, to brave modernity / Who needs Nelson or Churchill?

[16] In 2001, Lilley provoked some controversy in his party and Britain more widely by calling for cannabis to be legalised in a Social Market Foundation pamphlet.

[17] Lilley produced a report for the Bow Group in 2005 that was highly critical of Government plans to introduce national identity cards.

Lilley was at that time vice chairman and senior independent non-executive director of Tethys Petroleum and had received options to buy over $400,000 of shares at a price above their then market value.

[21] Further scrutiny came from the highlighting by Private Eye that Lilley had previously lobbied then climate change minister Ed Miliband with letters requesting the 'cost of global warming'.

[19] On 19 May 2016, Lilley, backed by other Eurosceptic Tory MPs as well as the other parties proposed a rebel amendment to the Queen's Speech, over fears that the US-EU pact would lead to the privatisation of the NHS by paving the way for American health providers in the UK.

The UK government ultimately agreed to amend the Queen's Speech to commit to explicitly protecting the NHS from the terms of the future trade deal.

[24] Following an interim report on the connections between colonialism and properties now in the care of the National Trust, including links with historic slavery, Lilley was among the signatories of a letter to The Telegraph in November 2020 from the "Common Sense Group" of Conservative Parliamentarians.