Although Blair defended his letter as simply "celebrating the success" of a British company, he was criticised because LNM was registered in the Dutch Antilles and employed less than 1% of its workforce in the UK.

[12] In 2004, Price announced his intention to begin a process of impeachment against Tony Blair following controversy over the Iraq War, with the backing of Plaid Cymru and SNP MPs as well as Boris Johnson and Nigel Evans.

[14] Price was ejected from the Commons chamber in 2005 after accusing the Prime Minister of having "misled" Parliament and then refusing to withdraw his comment, in violation of the rules of the House.

The SNP and Plaid Cymru motion proposing a committee of seven senior MPs to review "the way in which the responsibilities of government were discharged in relation to Iraq", was defeated by 298 votes to 273.

[16][17] Writing in the Welsh language current affairs magazine Barn in April 2007, Price criticised UK government policy on drugs, indicating his support for their legalisation under medical supervision.

However, the committee found that the three used this communication allowance improperly as part of Plaid's campaigning during the elections as the adverts were placed in publications with a circulation outside of their respective constituencies.

[22] Price has been a long-standing opponent to the war in Afghanistan and put forward an Early Day Motion calling for a timetable for withdrawal.

[9] In September 2010, he began studying at Harvard University, for a Master's in Public Administration and gaining a fellowship at the Center for International Development in the John F. Kennedy School of Government.

[37] In October 2018, Price revealed that he had recruited the SNP's former deputy leader Angus Robertson to oversee a review of Plaid Cymru's campaign strategy.

[41] At the 2019 general election, Plaid Cymru's manifesto titled 'Wales, It's Us' included policies such as a second Brexit referendum in which the party would campaign to remain in the European Union, investment in the development of environmentally friendly industry referred to as a 'green jobs revolution', more funding for education and police, drug law reform, greater devolution of powers over tax and giving the devolved administrations a veto over the UK going to war.

[44] In December 2020, Price promised that his party would hold a referendum on Welsh independence if it won a majority at the 2021 Senedd election though any such vote would need the agreement of the UK government.

[46] Price stated that he would form a government which would create a "fairer, greener future where our country thrives by taking control of its own affairs and unleashing its greatest potential – its people".

[47] The party made a net gain of one seat in that election with a slight reduction in its proportion of votes cast but lost second-place position to the Welsh Conservatives.

[48][49] In November 2021, Price and Welsh Labour leader Mark Drakeford reached a co-operation agreement on policy in a wide range of areas.

Acknowledging that he "no longer had the united support of [his] colleagues", Price stated that he would step down officially the following week, once the process for electing a new interim leader was finalised.