Six caravans arrived in the park yesterday afternoon at around 1.30pm.
A Worthing Borough Council spokesman said: “A welfare audit has been undertaken in relation to the travellers residing at Victoria Park in Worthing.
“A decision has been taken not to tolerate the travellers, save for one heavily pregnant woman and her immediate family.
“The remaining travellers have been served with a Notice of Direction to leave the site by tomorrow afternoon (Thursday).”
A welfare audit has also been carried out on those living in four vehicles on Goring Greensward, who also arrived yesterday.
They have been given the same deadline to leave.