Mr Howard wrote a character reference for the Catholic cardinal after he was convicted for child sex abuse.

"I am aware he has been convicted of those charges; that an appeal against the conviction has been lodged and that he maintains his innocence in respect of these charges," Mr Howard wrote about Pell.

"None of these matters alter my opinion of the cardinal."

Labor MP Anthony Albanese labelled the letter "very unfortunate".

"It made no reference at all to what had occurred, and it also suggested that his view of George Pell had not been changed," Mr Albanese said on the Today program.

"It does show a lack of judgment."

Mr Howard is not the only former prime minister to support the cardinal, with Tony Abbott calling Pell after the guilty verdict became public.

But Defence Minister Christopher Pyne said he couldn't comment on whether it was a mistake for Mr Howard to write the reference.

"I think John Howard wrote a character reference after the conviction of the cardinal for the sentencing, in terms of the sentence that Cardinal Pell might now receive," Mr Pyne said.

"Whether it was a good idea is really a matter for them to answer, not for me to answer."

Pell was found guilty in December of orally raping a 13-year-old boy and molesting another after Sunday mass at St Patrick's Cathedral in East Melbourne in 1996.

At the conclusion of a pre-sentence hearing on Wednesday, Pell was remanded in custody by County Court Chief Judge Peter Kidd.

Australian Associated Press