We have been in contact with the Conservative party since late March and have conducted an assessment of the information they have provided to us.
We are now satisfied that there are reasonable grounds to suspect that an offence or offences may have occurred. We will therefore continue this work as a formal investigation to establish whether this is the case.
The investigation will determine whether any transactions relating to the works at 11 Downing Street fall within the regime regulated by the commission and whether such funding was reported as required.
We will provide an update once the investigation is complete. We will not be commenting further until that point.
source: theguardian.com