The UPP proposed an alliance with the major liberal Democratic Party, which the Democrats rejected.[4]
In the 2012 National Assembly election the party gained eight seats for a total of thirteen seats out of 300, advancing to the third position, well ahead of the conservative Liberty Forward Party (which lost most of its seats).
On 24 April 2012, the party provisionally voted to drop the "Unified" component of its name, and adopt the name "Progressive Party". The change was subject to a vote of the party's Central Committee on 13 May.[14] On 3 May 2012, the party internal investigation revealed that wide-ranging irregularities occurred in selecting UPP's proportional representation candidates.[15][16] UPP won six proportional representatives in 11 April general election,[17] but one legislator resigned amid the election scandal. All four co-leaders of the party subsequently resigned on 12 May.[18]
The South Korean government petitioned the Constitutional Court of Korea to dissolve the UPP due to their alleged pro-North Korea views in November 2013, two months after the UPP members allegedly involved in the 2013 South Korean sabotage plot were arrested. On 19 December 2014 the Constitutional Court of Korea ruled 8–1 in favour of the dissolution. The five UPP lawmakers were also deprived of their National Assembly seats.[19][20] According to Amnesty International, the UPP's ban raised "serious questions as to the authorities' commitment to freedom of expression and association".[21][22][23]
Since the United Progressive Party was a big tent party until 2012 and before, there was no consistent ideology except for the motto of a "leftist" party. Before the 2012 party's controversy over fraudulent elections, the United Progressive Party was led by moderates, so some[who?] evaluated that "progressivism" was closer to "American (modern) liberalism" than "socialism".[24][25] However, after 2012, liberals and social democrats within the party left the party, and left-wing nationalists led the party much more, and afterwards were embroiled in controversy over allegations of being "far-left" or "pro-North Korea" (종북).[26]
On 5 September 2013, South Korea's intelligence agency, NIS, accused UPP lawmaker Lee Seok-ki of plotting a pro-North Korean rebellion. The case triggered a political and media firestorm in a nation where even praising the North can be considered a crime.[27] He allegedly led a May 2013 meeting, comprised partly of UPP members, in which reference was made to the prospect of attacking South Korean infrastructure in the event that recently heightened tensions between the Koreas led to war.
South Korean prosecutors subsequently indicted Lee on charges of plotting a pro-North Korea rebellion to overthrow the government, saying his plan posed a "grave" national security threat.[28] However, UPP lawmakers say that while the meeting in question did take place, they had no intention of destroying South Korean government infrastructure.[citation needed]
On 17 February 2014, Lee was sentenced by a district court to 12 years in prison.[29]
^Chung Min Lee, ed. (2016). Fault Lines in a Rising Asia. Brookings Institution Press. p. 323. ISBN9780870033131. The far-left Unified Progressive Party (UPP) was South Korea's most pro–North Korean political party, and its leadership was in near-perfect alignment with the policies espoused by North Korea, but it was disbanded when the ...
^노회찬, 심상정, 유시민 통합진보당 탈당: 민노당 전 최고위원, 지방의원, 참여계 당원 3000여명도 '탈당 러시' [Roh Hoe-chan, Sim Sang-jung, and Yoo Si-min left the Unified Progressive Party: About 3,000 former supreme council members, local councilors, and participating members of the DLP are also leaving the party.]. Pressian. 13 September 2012. Retrieved 4 December 2021.
^Huh Yun-seok(허윤석) (3 May 2012). '지도부 사퇴' 밝힌 진보당, 비례대표 거취 '충돌' [UPP party leader resigned. Internal conflict is widening.]. SBS (in Korean). Retrieved 3 May 2012.
^보수적인, 너무나 보수적인 우리의 '진보' [Conservative. Our "progressive" that's too conservative.]. Pressian. 1 December 2011. Retrieved 4 December 2021.
^"UPP's biggest faction denies rigging". Korea JoongAng Daily. 7 May 2012. Retrieved 2 January 2022. The internal strife in the liberal Unified Progressive Party continued with the leader of the party's largest faction demanding a vote on whether the candidates elected in a rigged primary should step down.