Victorian Liberal MP Sam Groth has quit the frontbench in a move which may destabilise state Opposition Leader John Pesutto’s leadership.

Liberal MP Sam Groth has resigned from shadow cabinet, saying he can no longer serve in John Pesutto’s front bench.

Sam Groth has resigned from the Liberal Party frontbench, a further sign of turmoil in the Victorian Liberal Party following John Pesutto’s devastating defamation lawsuit loss.

The Liberal MP for Nepean, former tennis player Sam Groth, has issued a statement saying he's resigning from the Victorian opposition's frontbench.

Victorian Liberal frontbencher Sam Groth has stunned his colleagues by quitting the frontbench, piling pressure on John Pesutto over the defamation crisis crippling his leadership.