South Thanet MP Craig Mackinlay and two staff have appeared at Westminster Magistrates Court to answer charges of illegal election expenditure during the 2015 General Election.
Mr Mackinlay, 50, election agent Nathan Gray, 28, and party activist Marion Little, 62, have each been charged with offences under the Representation of the People Act 1983.
All three pleaded not guilty to the charges.
The accusations relate to a Channel 4 investigation which questioned the local election spend during the Conservative campaign.
The legal expense limit for South Thanet for that time-frame was £15,016.38. The Conservatives’ local expense declaration was for £14,837.
But a bill of more than £18,000 for stays in two isle hotels and a hostel was not included on local expenses but attributed to national spending. This figure would have taken the party over the legal campaign limit.
The trio will next appear at Southwark Crown Court on 1 August.
The maximum sentence Mr Mackinlay could face if convicted is one year in prison or a fine.