Marek was elected a member of Ceredigion District Council in 1979 and served until 1983; he was chair of its finance sub-committee in the year 1982–83. Having previously unsuccessfully contested
Ludlow in
October 1974, Marek was elected as
Labour Party Member of Parliament for the
Wrexham Westminster constituency in
1983 and served as a party spokesman on Treasury matters, although he was not offered a government post in 1997. Marek then stood as a candidate for the
John Marek Independent Party and defeated the official Labour Party candidate,
Lesley Griffiths, a former secretary of his, by 973 votes. Later that year he formed a new political party called
Forward Wales (). He ran for re-election in the
2007 Welsh Assembly election, but was defeated by Labour's Lesley Griffiths by 1,250 votes, thanks to a swing to the Conservatives,
Liberal Democrats, and
UKIP. On 29 March 2010, Marek joined the
Conservative Party, Marek is one of three Welsh MPs or AMs to win a constituency as both a party candidate and an independent, following
S. O. Davies who was MP for
Merthyr Tydfil from 1934 until his death in 1972, who was deselected by the local
Labour Party on grounds of age prior to the
1970 general election but ran against the official candidate as an independent and won; and
Peter Law who was barred from contesting his seat for Labour due to an
all-woman shortlist being imposed ==Wrexham AFC==