Is it safe for a portacot to have a mosquito net covering it? My child (16month) goes to their grandparents once a week and has started to attempt to climb out of the portacot she sleeps in when there. They want to buy a mosquito netting to cover it to prevent this. I think she would just pull it down and break it so am not keen, but even if not, is it safe for the netting to cover the cot when sleeping?

For safety reasons, Red Nose recommends that once a child is climbing (or looks like climbing) out of a cot then the child needs to be moved to a bed (or floor mattress) for sleep.
If your child is climbing out of the porta cot, there is also a risk to the integrity of the porta cot, where the sides may be damaged or collapse as a result.
It is most unlikely that a mosquito net would stop child climbing (or attempting to climb) out of the cot.
There are also risks of her pulling it down & may become entangled in it.

Red Nose has this information about porta cots. Some toddlers are too heavy for some porta cots.
Do not use a portable cot if your child weighs more than 15kg (or check instructions of your particular model).
https://rednose.org.au/article/portable-cots