The Probation Inspectorate said it is particularly concerned that a desire to avoid delays during court proceedings is taking priority over gathering vital information related to the safety of children.
Its inspection of probation services in the capital found that courts are proceeding with sentencing before children's services are able to respond to requests for information relating to child safety.
The inspectorate said such information could have a significant impact on sentencing and help probation services ensure that children's safety is taken into account.
"Court officers asked children's social care services for information about a case, knowing that they were unlikely to receive a response within the time available at court and the case would proceed to sentence the same day," the inspectorate's report into the effectiveness of probation work in the capital states.
"These checks might reveal information that potentially would have altered the sentencing outcome, allocation or initial planning."
The report adds: "There was clearly a tension between avoiding unnecessary delays in sentencing and making sure that risk of serious harm was assessed accurately from the outset.
"Our view is that the safety of known partners and children should take priority."
The inspectorate also raises concerns about children's safeguarding training for probation staff.
A number of staff said that they had yet to complete this training, despite it being a mandatory requirement for operational staff and line managers.
Inspectors found a raft of examples where lack of training is leading to probation services failing to properly assess risks to children.
One inspector, observing the performance of a probation officer working with an offender in a domestic violence case, said: "No safeguarding checks were made even though they were aware he (the offender) had children. The report did not mention risks to children and how they were to be kept safe."
The inspectorate also found that probation services are particularly struggling to access child protection information when families involved lived across a number of boroughs.
"We constantly must renegotiate with different children's social care services," one senior probation officer told inspectors.
"They have different databases, families live across several boroughs, it's complex."
Dame Glenys Stacey said that while the overall court work was carried out well, inspectors found staff to be "particularly hampered by a lack of access to information on child and adult safeguarding".
She added that while there were encouraging signs of improvement in probation services, "more still to be done".