Some traders say it is possible for a cartel of brokers to get together and take up huge positions through circular trading in a way that the marketwide limit in a security is breached.
That makes it impossible for new traders to sell the futures even if they feel the rise in a company’s stock price is unjustified.
This helps keep the stock price firm.
Also, traders with existing short positions in the derivatives segment will be forced to cover their positions at a higher price, pushing the stock price even higher.-from Money Control