The Transport Select Committee said the decision to proceed with a 4,000-space park in Kent was taken "hastily" by the government.
Two sites the "same size as Disneyland in California" are being considered.
It comes after part of the M20 was used 32 times last summer by queuing lorries - a process known as Operation Stack.
The Department for Transport (DfT) said the preferred location for a "permanent solution" would be chosen soon.
The committee said in its report the government "has not demonstrated clearly enough what options have been evaluated".
It listed possible alternatives including upgrading the M20 and/or the A2/M2, increasing the capacity of cross-Channel services, or building a network of smaller lorry parks.
Labour MP Louise Ellman, chairman of the committee, said: "We are not saying the government should not press ahead with its proposal, only that it has more work to do to persuade us of the business case for this investment."
Kent County Council told the committee disruption caused by Operation Stack cost the local economy £1.5m per day.
Last week Highways England awarded a contract to Balfour Beatty to build the park at one of two suggested sites north of the M20, near the village of Stanford.
A spokesman for the DfT said: "It is right we find a permanent solution and we are determined to keep Kent moving.
"Highways England received more than 1,000 responses to its public consultation on this issue and will announce a decision on the preferred site soon."
It is anticipated the park will be partially open by summer 2017.
Ministers need to justify their case for a "gargantuan" £250m lorry park put forward to ease disruption caused by cross-Channel services, MPs have said.