George Hollingbery met with campaigners on Friday who were frustrated with 'anti-social motorbike noise' that he said 'blights the lives' of people near the A32 and A272 in the Meon Valley.
Police and Hampshire County Council have been involved in trying to cut down on the problem.
But political opponents have accused theÂ Meon Valley MPÂ of wrongdoing after he sent out a detailed two-page letter on House of Commons headed stationery.
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In the letter he called the problem 'the most intractable and difficult issue' he has experienced since becoming an MP in 2010.
Liberal Democrats complained to the Parliamentary Commissioner for Standards as the letter was sent out in the run up to theÂ by-election for Winchester City Council, which was held yesterday.
Mr Hollingbery has distributed the letter in Bishop's Waltham and other areas, aiming to deliver it to nearly 9,000 homes.
Martin Tod, from Winchester Lib Dems, said: 'These letters alone are likely to have have cost the taxpayer more than the other parties are even allowed to spend in the by-election in total.'
But the MP has hit back and said the complaint is nonsense.
He said: 'This complaint is utter nonsense and nothing more than political mischief making by the Lib Dems.
'The fact is I have written to 8,945 households in three wards along the A272 and A32 in my constituency to keep them up to date on the serious issue of motorcycle noise.
'These letters, which make no mention of any election campaign or any candidate, have either been delivered or will be delivered in the coming days.
'They were firstly delivered to two wards '“Â Central and Upper Meon Valley '“Â because that is where I have received the most complaints about motorcycle noise.
'As it stands, I have delivered to most of the Upper and Central Meon Valley Wards and some of Bishop's Waltham.
'It is perfectly legitimate for me to communicate officially with my constituents on a major local issue that affects many people. There cannot be a purdah to stop me doing so and to suggest otherwise is totally wrong.'
Electors were voting in the Upper Meon Valley by-election yesterday. The watchdog does not comment on investigations into named MPs.