[7][8] Influenced by the growth of Cornish nationalism in the first half of the twentieth century, Mebyon Kernow formed as a pressure group in 1951.

In the 1970s, MK became a fully-fledged political party, and since then it has fielded candidates in elections to the House of Commons and the European Parliament, as well as local government in Cornwall.

[16] Early members of MK cited their absence from Cornwall during their university years and the war as instrumental in the formation of their Cornish identity.

[20] At the party's inaugural meeting, held at the Oates Temperance Hotel in Redruth,[20] thirteen people were present and a further seven sent their apologies.

It highlighted the high proportion of executives in local government which were not Cornish and campaigned against inward migration to Cornwall from the rest of the United Kingdom.

[23] Charles was replaced by Major Cecil Beer, a former civil servant who sought to reunify the Cornish nationalist movement.

[36] In April 1967, Colin Murley was elected for MK onto Cornwall County Council for the seat of St Day & Lanner; he had stood on an anti-overspill platform.

The decision meant that councillors, prospective parliamentary candidates and MPs who held dual party membership began to disassociate themselves from MK.

[42] The CNP's formation highlighted deep fissures in MK between its constitutionalist and separatist wings; these were exacerbated by continuing inward migration to Cornwall, leading to a 26% increase in its population in the two decades to 1981.

[55] Citing concerns about its effect on Cornwall's fishing industry, the party opposed the Common Market;[56][57] MK only began to endorse the UK's membership of the EEC in the 1980s.

[60] While the infighting consolidated MK's economic stance as left-of-centre, the party's everchanging positions confused voters and presided over the decline of its magazines, including the Cornish Nation.

[47] During this period, the party focussed on its opposition to the creation of a South West England region[5] and the construction of a nuclear station at Luxulyan;[56] this latter campaign culminated in the formation of the Cornish Anti-Nuclear Alliance, which drew over 2,000 attendees to its first rallies in Truro in July 1980.

[67] The campaign called for an exclusively-Cornish European Parliament constituency and was founded on MK's long-standing opposition to amalgamating public boards and companies in Cornwall and Devon, a process which had steadily increased during the decade.

[47] Jenkin, who stood as the party's candidate, campaigned on a platform opposing out-of-town developments and a second Tamar crossing, and calling for greater Cornish representation in Europe.

[78] One of Cole's earliest actions as leader was to launch the Cornish Millennium Convention on 8 March 1998, coinciding with protests at the closure of South Crofty, Cornwall's last working tin mine.

[79] However, the Convention's launch was eclipsed by the formation of Cornish Solidarity, a pressure group involved in direct action which grew from the South Crofty protests and had similar aims as MK.

[9] The party did not contest the 1999 European Parliament election, given the size of the new South West England constituency and the large prerequisite £5,000 deposit.

[20] A delegation including Cole, Andrew George, then the Liberal Democrat MP for St Ives, and representatives of the Convention presented the Declaration to 10 Downing Street on 12 December 2001.

[90] In August 2008 MK deputy leader, Conan Jenkin, expressed Mebyon Kernow's support for a proposed legal challenge by Cornwall 2000 over the UK Government's exclusion of the Cornish from the Framework Convention for the Protection of National Minorities.

[citation needed] However the fund failed to meet the required target of £100,000 by the end of December 2008, having received just over £33,000 in pledges, and the plan was abandoned.

MK "accused the coalition government of treating Cornwall with "absolute contempt" as a result of this, stating that Prime Minister David Cameron and Deputy Prime Minister Nick Clegg had "devised the bill to breach the territorial integrity of Cornwall", and that it broke election promises from their parties to protect Cornish interests.

[97] Cameron replied to concerns by stating that "it's the Tamar, not the Amazon, for Heaven's sake"; his controversial remark was widely ridiculed in Cornwall.

[106] It also did not stand candidates in the 2019 European Parliament election,[107] but its leadership endorsed the Green Party because of their historic cooperation, support for a Cornish Assembly and other similar policies.

[108] At a Policy Forum on 22 June 2018, Mebyon Kernow launched an updated version of its campaign publication titled "Towards a National Assembly of Cornwall.

It emphasises Cornwall's distinct Celtic culture and language, as well as its border along the River Tamar, which has largely remained unchanged since 936 AD.

[115][116] The party regularly highlights problems with the Cornish economy: Cornwall has lower wages and higher unemployment than the rest of the United Kingdom.

[120][121] Mebyon Kernow wants to break up the SWRDA into small county areas and implement a Cornish Regional Development Agency.

MK is run on a day-to-day basis by a 20-member National Executive, which includes the leadership team, policy spokespersons, and local party representatives.

[147] In 1979, in the first elections to the European Parliament, Mebyon Kernow's candidate Richard Jenkin was able to attract more than five per cent of the vote in the Cornwall seat.

[149] Since 2009, MK has not stood candidates in European Parliament elections, given the difficulties of winning a seat in a constituency encompassing electorates outside Cornwall.