Speaking to the Western Morning News during a visit to Cornwall, the Deputy Prime Minister said the coalition could "do more" to prevent a repeat of the region being cut off from the rest of the country.
See a picture gallery of Nick Clegg's visit to Cornwall.He also responded coolly to a Tory plan to wipe the Lib Dems off the electoral map in Devon and Cornwall, arguing his party offered a commitment to "fairness" that his coalition partner could not.
The Lib Dem leader's promise to look at protecting the mainline – which was seriously blocked on three occasions before Christmas – comes after the Western Morning News revealed rail bosses are reviewing 40 trouble spots.
Mr Clegg said: "The spectre of the flooding begs big questions about how we protect that umbilical transport link between Cornwall and the rest of the country.
"I think it's very important Network Rail follow up its commitment to looking at the 40-odd vulnerable pinch points which the recent floodings have highlighted once again.
"I can't second-guess what Network Rail is going to come up with, but I can certainly confirm that in government we are working very closely to try to make sure within available funds we can do more to protect the main railway line from being submerged in flood water."
Asked whether it was unacceptable that a vast swathe of the country was inaccessible for long periods, he said: "I totally accept we need to do more to prevent that from happening."
This week, the WMN revealed the Conservative Party is targeting ten Lib Dem seats in the next election in the South West – including all five in Devon and Cornwall. Mr Clegg said it is "no surprise", adding: "We'll do the same."
The election battle will be a straight fight between Lib Dems and Tories across much of the region after Labour revealed it would be targeting just one gain, in Plymouth, and nothing in Cornwall.
While the Lib Dems have been battered in recent by-elections, thanks to unpopular cuts and a broken promise on university fees, Mr Clegg argued support had held up in areas where they have a strong local presence.
Of holding seats, he said: "Our record speaks for itself. We have three of the six Cornish constituencies. We have a long history of serving Cornwall and we've got three absolutely outstanding MPs."
He added the party had curbed the Tories in government, who in turn have blocked Lib Dem plans for a "mansion tax" on the wealthy. He said: "Frankly, if it wasn't for the Liberal Democrats in government you wouldn't be doing a lot of the fair things we are doing.
"We wouldn't be taking low paid people out of paying income tax. We wouldn't be providing the pupil premium. We are the ones in government delivering the huge number of apprenticeships.
"We would like to have gone further. We believe there is a case for a mansion tax – millionaires in Kensington chipping in a bit extra to help people in Cornwall. The Conservatives blocked that.
"If we were alone in government we would have got tougher on the banks sooner. We are the only party that strikes the balance between tackling the economy and a fairer society."
To ram home the message, Mr Clegg yesterday visited Penwith College in Penzance to underline investment in apprenticeships, before visiting the A30 that is to be dualled near Bodmin following Government backing, and later Brannel school near St Austell to champion extra investment for poor school children.
He said he was "not going to make great lofty claims" but hopes to make "progress" at the next election.
Of Labour, he said: "Labour have turned their backs on Cornwall. If you're someone who doesn't feel favourably disposed towards the Conservatives there is only one choice. It shows how important it is to have a Liberal Democrat voice in your area."
