The Liberal Democrats have said GDP shrinking more than expected in April shows the government needs to "listen" and change course.
Reacting to the data, Daisy Cooper said: "Today's figures should be a wake-up call for the government which has so far refused to listen to the small businesses struggling to cope with the jobs tax, worried that our high streets will be completely hollowed out and that our hospitality sector is hanging by a thread."
The jobs tax refers to the chancellor's decision to hike employer national insurance contributions (NICs).
Reeves has called the 0.3% fall in GDP "disappointing", though she conceded she wasn't entirely surprised by the decrease because of global uncertainty, such as the imposition of tariffs by the US.
Cooper, who is the party's Treasury spokesperson, added that the government "must stop cowering in the corner" due to the tariffs, and should instead create "an economic coalition of the willing" with European and Commonwealth nations.
She also repeated the Lib Dems calls for the hike to NICs to be reversed and for a bespoke EU-UK customs union.