Ms Haigh said: “I am pleased to see immediate improvements being made at Euston station to reduce the risk of overcrowding, drive up standards and deliver a better experience for passengers.
“For too long, Euston station simply has not been good enough.
She added work was under way on a “long-term solution for the station”.
Plans to redevelop Euston include the creation of a larger concourse, but these are subject to Network Rail securing more government funding.
Major work to prepare a site alongside the station for HS2 was halted by the Conservative government in March last year.
Labour ministers have yet to announce whether the high-speed railway will be extended to Euston or will only run to and from Old Oak Common in the west London suburbs.
London Northwestern Railway customer experience director Jonny Wiseman said: “We’ll be monitoring the impact of these changes closely as we continue working with partners to make the process of boarding trains smoother across the station.”