The Parliamentary standards watchdog has begun an inquiry into Bristol NW Conservative MP Charlotte Leslie over political donations.
Last month she apologised to the Commons for failing to register more than £20,000 in donations to her local party from the boss of the Bristol Port company.
She later spoke in debates about the proposed Severn Barrage, which the company opposes, without referring to the donations.
A Bristol MP could face an investigation over her failure to declare cash donations to her local party.
Charlotte Leslie the Conservative member for Bristol North West apologised to the House of Commons earlier this month for failing to comply with the rules. But now a letter of complaint has been made to the Westminster Standards Watchdog.
Ms Leslie asked questions about the proposed Severn barrage but failed to mention that her local party had received £17,000 from the boss of the Bristol Port Company, which opposes it.
The Government has today backed a report which casts serious doubt over plans for a giant barrage across the Severn Estuary.
Ministers have agreed with a committee of MPs who said they could not recommend the £25 billion scheme.
The company behind the plans claims a barrage from Brean Down to South Wales could produce five per cent of the UK's energy.
But the committee says it's failed to provide enough evidence about what subsidies it would need, the impact on the environment, and potential job losses at the port of Bristol.
The news has been welcomed by environmentalists and wildlife experts.
Hafren Power, the company set up by investors hoping to build and operate the Severn Estuary barrage, has announced that five global companies are now working on the project.
They have expertise in engineering, construction, project management and logistics and are working with Hafren Power on its proposal to build a £25 billion, 18km (11 mile) electricity generating barrage across the Severn estuary.
Arup, Bechtel, DHL, Mott MacDonald and URS are currently assessing what will be required to manage the planning consents and environmental approval processes.
If the Barrage eventually gets the go-ahead, the nine-year build would be the biggest British infrastructure project since the Channel Tunnel.
A government minister has cast doubt on whether the proposed Severn barrage should go ahead.
A private consortium wants to build a £25 billion barrage between Weston-super-Mare and Cardiff, though it would require government support.
Hafren Power claims it could generate 5% of the country's energy from the tidal power harnessed.
But today the Energy Minister Greg Barker MP told MPs more work needed to be done to establish the costs and impact it would have on wildlife and the port of Bristol.
A former Minister has urged the Government to get behind the Severn Barrage project.
It would cost a staggering twenty five billion pounds - of private sector money - and according to former Welsh Secretary Peter Hain, would generate five per cent of the country's entire electricity from tidal power.
However it's strongly opposed by conservation groups - who say it would damage internationally-protected mudflats - and by the port of Bristol. Today MPs heard both sides of the argument, as our political correspondent Bob Constantine reports.
Three British men, including two former soldiers from the region, have been badly injured in South America while taking part in the Dakar Rally, said to be the world's toughest event of its kind.
Falklands War Veteran Lee Townsend from Yate in South Gloucestershire and retired army major John Winskill from Durrington in Wiltshire are in a stable condition in hospital. They were travelling in a support vehicle involved in a head on crash in Peru. Two other people are thought to have died.
Andy Richards of the Unite union says there is "significant" public support in Wales for the Severn barrage. He said it was time to move on from the "scaremongering" and start to examine the detail of the proposal by Hafren Power, the firm behind the scheme.
Labour MP Peter Hain, told the Energy and Climate Change Committee that the prospect of a Severn barrage has been 'studied to death' and it's time it all went ahead. He said the project would create 50,000 jobs and provide flood protection to 90,000 properties.
Simon Bird, the boss of the Bristol Port Company has told a committee of MPs that building a barrage across the Severn estuary could be a "killer" to his business.