Question: What is the name of this centre-left political party in the United Kingdom, in which Gavin Shuker serves as the Chair?

Context paragraphs:
Militant Socialist Movement: The Militant Socialist Movement (French: "Mouvement Socialiste Militant" ; abbreviated MSM) is a centre-left political party in Mauritius that adheres to the philosophies of socialism and political democracy.  It is the largest single political party in the National Assembly of Mauritius, winning 34 of the 69 seats in the 2014 general elections.  With political development, 6 MPs from the opposition joined officially the party making the current majority at 40.  It also holds the largest number of seats in all city/town councils through the country with 60 councilors out of 120.

Labour Party (UK): The Labour Party is a centre-left political party in the United Kingdom.  It has been described as a broad church, bringing together an alliance of social-democratic, socialist and trade-unionist outlooks.  The party's platform emphasises greater state intervention, social justice and strengthening workers' rights.  Labour is a full member of the Party of European Socialists and Progressive Alliance, and holds observer status in the Socialist International.

Social Democratic Union of Macedonia: The Social Democratic Union of Macedonia (Macedonian: Социјалдемократски сојуз на Македонија –СДСМ, SDSM) is a social-democratic and main centre-left political party in Macedonia.  The Social Democratic Union of Macedonia was founded on 20 April 1991 at the 11th Congress of SKM-PDP (UCM – Party for Democratic Changes).  Branko Crvenkovski was elected as the party's first president.  Its current leader is Zoran Zaev.  The Social Democratic Union of Macedonia is a member of the Progressive Alliance and an associate affiliate of the Party of European Socialists (PES).  SDSM is a centre-left positioned political party with social democratic ideology.

Co-operative Party: The Co-operative Party is a centre-left political party in the United Kingdom supporting co-operative values and principles.  Established in 1917, the Co-operative Party was founded by co-operative societies to politically campaign for the fairer treatment of co-operative enterprise and to elect co-operators to Parliament.  The Party’s roots lie in the Parliamentary Committee of the Co-operative Union established in 1881.

Democratic Party &quot;Saimnieks&quot;: The Democratic Party "Saimnieks" (Latvian: "Demokrātiskā partija "Saimnieks"" ) was a Latvian centre-left political party formed through the merger of the Latvian Democratic Party and the political party "Saimnieks" in 1995.  It won the 1995 parliamentary election and was represented by 18 deputies in the 6th Saeima.  It participated in Andris Šķēle's first and second cabinet, withdrawing from the coalition in 1998.

Portuguese Democratic Labour Party: Portuguese Democratic Labour Party (in Portuguese: "Partido Trabalhista Democrático Português") was a centre-left political party in Portugal.  PTDP was founded on May 3, 1974, the first political party to be formed after the Carnation Revolution.  PTDP didn't make much impact however, and the party was never legally registered.

National Party of Scotland: The National Party of Scotland (NPS) was a centre-left political party in Scotland which was one of the predecessors of the current Scottish National Party (SNP).  The NPS was the first Scottish nationalist political party, and the first which campaigned for Scottish self-determination.

Milanka Opačić: Milanka Opačić (; born 17 April 1968) is a Croatian politician who served as a Minister of Social Welfare and Youth at centre-left Cabinet of Zoran Milanović from 2011 to 2016.  She served as one of four vice-presidents of the Social Democratic Party of Croatia, the main centre-left political party in the Croatian Parliament.  She was first elected to Parliament in 1992 parliamentary election, and was reelected in 2000, 2003, 2007, 2011, 2015 and 2016.  She currently serves as Vice president of the Croatian Parliament.

Gavin Shuker: Gavin Shuker (born 10 October 1981) is an English Labour Co-operative politician, who has been the Member of Parliament (MP) for Luton South since 2010.  Shuker successfully defended the seat after his predecessor Margaret Moran stood down following controversy over her expenses.  Shuker serves as Chair of the Parliamentary Co-operative Party and in 2013 he was appointed as a Shadow International Development Minister.

Movement for Multi-Party Democracy: The Movement for Multi-party Democracy (MMD) is a political party in Zambia.  Originally formed to oust the previous government, MMD controlled an absolute majority in parliament between 1991 and 2001, when its past leader, Frederick Chiluba was President of Zambia.  Its election into power in 1991 ended the 27-year rule of President Kenneth Kaunda and his United National Independence Party (UNIP).  It remained the dominant party within Zambian politics until the general elections of September 2011.  It is a centre-left political party.

Supporting paragraphs: Gavin Shuker Co-operative Party
Answer: Co-operative Party