Rail operators are being urged not to overcharge passengers as volcanic ash causes travel chaos across Europe.
Prices have gone up considerably since all air traffic was grounded in Western Europe on Thursday with single tickets form London to Paris costing £223 ($340) compared to the usual £69 ($105).
Eurostar is fully booked until Tuesday and is dealing with 50,000 more passengers than normal.
Eurotunnel journeys from Folkstone to Paris have also risen from £53 ($81) to £147 ($224).