“At the centre of this horrific event, there is still a family and community grief that is raw; a pain that not even justice can ever truly heal,” he said.
“Although no words today can ever truly convey the depths of that pain, I want the families to know that our thoughts are with them and everyone in Southport affected by this barbaric crime.
“The whole nation grieves with them.”
Conservative leader Kemi Badenoch has also said there are questions to answer about the case.
In a social media post, she said: “We will need a complete account of who in government knew what and when. The public deserves the truth.”
Rudakubana is due to be sentenced on Thursday and is expected to be given a life sentence.
However, he cannot be sentenced to a whole-life term for his crimes because he is under the age of 21.
