Actually there are two working conditions which lead to opposition of the labour unions.
First: The first demand of labour union was the low wages and contractual employment. The Labour demanded that the wages should be high and that the nature of employment should be permanent rather than contractual.
Second: The second opposition of labor unions was actually raised by skilled workers concerning about the very small wages differential in skilled and unskilled labour. They sought that the wages paid to skilled workers should be significantly more than that of unskilled one.