The firm ordered the vehicles through Cameron Clarke Leasing, based in Lancashire, which is a member of the Lex Vehicle Partners network.
The 15 adapted Vauxhall Vectras and Astras are the first alternative fuel vehicles that Cameron Clarke has supplied.
Tony Cameron, a CCL partner, said: 'These Vauxhall cars are what many companies have been wanting. With LPG capability built-in, they are better engineered and more space-efficient than cars with a retro-fitted tank.'
Richard Parker, company director of Tom Parker, which has a workforce of 58, said: 'The vehicles offer considerably lower running costs and lower tax bills for the sales team. They are also better for the environment.
'It was important for us to deal with a local company rather than a huge multi-national. We felt we could get a more personal service and we have been proved right.'
Cameron Clarke is one of 23 leasing partners in the network, which is the small leasing division of Lex Vehicle Leasing.