Conservative vice-chairman Michael Fabricant said the party's voice was "muffled" and unclear following the defeat in the Eastleigh by-election.
The MP took to Twitter to argue that the party needed to "simplify its message":
#Eastleigh The Conservative voice is muffled and not crisp. It does not clearly project Conservative core policies or principles.
#Eastleigh The Cons Party must now co-ordinate & simplify its message without policy distractions away from core principles. 26 months
#Eastleigh Everyone from the PM downwards must focus on the economy, immigration, crime, Europe and not allow other side policies distract
More top news
The Islamic centre where the Manchester suicide bomber is thought to have prayed says the attack "has no place in Islam or any religion".
German chancellor Angela Merkel and Indian prime minister Narendra Modi among those to praise "great spirit" of Manchester people.
The bomber's identity has been confirmed by Greater Manchester Police.