evidence: Sir Jeffrey Donaldson is the DUP's Westminster leader and is currently the longest-serving MP from Northern Ireland. [...] Sir Jeffrey continued to disagree with Lord Trimble, which eventually led to his leaving the party in 2003 and joining the DUP in 2004. , external [...] Edwin Poots has been a member of the DUP for all of his political career and is currently the minister for agriculture, environment and rural affairs.