Transport secretary Philip Hammond said the changes would “significantly mitigate” the impact of the 250mph trains on towns and villages bordering the railway.
The proposed line passes through the constituencies of several Tory MPs, including those of Welsh Secretary Cheryl Gillan and Andrea Leadsom, MP for South Northamptonshire, who questioned whether the proposals represented value for money.
Leadsom said: “My overriding belief is this is wrong. The UK is simply too small, hilly and contoured to cope with a 250mph juggernaut.”
Hammond insisted the scheme would bring parts of the country closer together by reducing journey times to and from London.
But he acknowledged that some along the preferred route may suffer falls in the value of their homes and said the government was considering compensation.
Hammond said engineers would reduce the environmental impact of the railway line by running it through tunnels and cuttings.
The coalition has changed about half the plan originally put forward by the body charged with designing it, HS2 Ltd.
A line between London and Birmingham and a connection to the Channel Tunnel rail link – known as HS1 – will be built first, with a y-shaped network stretching to Manchester and Leeds to be built later, as well as a branch to Heathrow Airport.
Track and station operator Network Rail said the new line was needed to relieve congestion on the existing West Coast main line and provide extra space for passenger and freight trains.
The Confederation of British Industry said it backed the route chosen by ministers because it would bring more benefits for the economy and better connections for big cities.